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[2.35.55.161]) by smtp.gmail.com with ESMTPSA id l10-20020a1ced0a000000b003c409244bb0sm134337wmh.6.2022.10.20.08.26.53 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Oct 2022 08:26:53 -0700 (PDT) From: Paolo Valente To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, glen.valante@linaro.org, arie.vanderhoeven@seagate.com, rory.c.chen@seagate.com, Paolo Valente , Gabriele Felici , Carmine Zaccagnino Subject: [PATCH V4 1/8] block, bfq: split sync bfq_queues on a per-actuator basis Date: Thu, 20 Oct 2022 17:26:36 +0200 Message-Id: <20221020152643.21199-2-paolo.valente@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20221020152643.21199-1-paolo.valente@linaro.org> References: <20221020152643.21199-1-paolo.valente@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747220887271716400?= X-GMAIL-MSGID: =?utf-8?q?1747220887271716400?= Single-LUN multi-actuator SCSI drives, as well as all multi-actuator SATA drives appear as a single device to the I/O subsystem [1]. Yet they address commands to different actuators internally, as a function of Logical Block Addressing (LBAs). A given sector is reachable by only one of the actuators. For example, Seagate’s Serial Advanced Technology Attachment (SATA) version contains two actuators and maps the lower half of the SATA LBA space to the lower actuator and the upper half to the upper actuator. Evidently, to fully utilize actuators, no actuator must be left idle or underutilized while there is pending I/O for it. The block layer must somehow control the load of each actuator individually. This commit lays the ground for allowing BFQ to provide such a per-actuator control. BFQ associates an I/O-request sync bfq_queue with each process doing synchronous I/O, or with a group of processes, in case of queue merging. Then BFQ serves one bfq_queue at a time. While in service, a bfq_queue is emptied in request-position order. Yet the same process, or group of processes, may generate I/O for different actuators. In this case, different streams of I/O (each for a different actuator) get all inserted into the same sync bfq_queue. So there is basically no individual control on when each stream is served, i.e., on when the I/O requests of the stream are picked from the bfq_queue and dispatched to the drive. This commit enables BFQ to control the service of each actuator individually for synchronous I/O, by simply splitting each sync bfq_queue into N queues, one for each actuator. In other words, a sync bfq_queue is now associated to a pair (process, actuator). As a consequence of this split, the per-queue proportional-share policy implemented by BFQ will guarantee that the sync I/O generated for each actuator, by each process, receives its fair share of service. This is just a preparatory patch. If the I/O of the same process happens to be sent to different queues, then each of these queues may undergo queue merging. To handle this event, the bfq_io_cq data structure must be properly extended. In addition, stable merging must be disabled to avoid loss of control on individual actuators. Finally, also async queues must be split. These issues are described in detail and addressed in next commits. As for this commit, although multiple per-process bfq_queues are provided, the I/O of each process or group of processes is still sent to only one queue, regardless of the actuator the I/O is for. The forwarding to distinct bfq_queues will be enabled after addressing the above issues. [1] https://www.linaro.org/blog/budget-fair-queueing-bfq-linux-io-scheduler-optimizations-for-multi-actuator-sata-hard-drives/ Signed-off-by: Gabriele Felici Signed-off-by: Carmine Zaccagnino Signed-off-by: Paolo Valente Signed-off-by: Gabriele Felici Signed-off-by: Carmine Zaccagnino Signed-off-by: Paolo Valente --- block/bfq-cgroup.c | 95 ++++++++++++++++------------- block/bfq-iosched.c | 141 +++++++++++++++++++++++++++----------------- block/bfq-iosched.h | 51 ++++++++++++---- 3 files changed, 183 insertions(+), 104 deletions(-) diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index 144bca006463..d243c429d9c0 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -700,6 +700,48 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, bfq_put_queue(bfqq); } +static void bfq_sync_bfqq_move(struct bfq_data *bfqd, + struct bfq_queue *sync_bfqq, + struct bfq_io_cq *bic, + struct bfq_group *bfqg, + unsigned int act_idx) +{ + if (!sync_bfqq->new_bfqq && !bfq_bfqq_coop(sync_bfqq)) { + /* We are the only user of this bfqq, just move it */ + if (sync_bfqq->entity.sched_data != &bfqg->sched_data) + bfq_bfqq_move(bfqd, sync_bfqq, bfqg); + } else { + struct bfq_queue *bfqq; + + /* + * The queue was merged to a different queue. Check + * that the merge chain still belongs to the same + * cgroup. + */ + for (bfqq = sync_bfqq; bfqq; bfqq = bfqq->new_bfqq) + if (bfqq->entity.sched_data != + &bfqg->sched_data) + break; + if (bfqq) { + /* + * Some queue changed cgroup so the merge is + * not valid anymore. We cannot easily just + * cancel the merge (by clearing new_bfqq) as + * there may be other processes using this + * queue and holding refs to all queues below + * sync_bfqq->new_bfqq. Similarly if the merge + * already happened, we need to detach from + * bfqq now so that we cannot merge bio to a + * request from the old cgroup. + */ + bfq_put_cooperator(sync_bfqq); + bfq_release_process_ref(bfqd, sync_bfqq); + bic_set_bfqq(bic, NULL, 1, act_idx); + } + } +} + + /** * __bfq_bic_change_cgroup - move @bic to @bfqg. * @bfqd: the queue descriptor. @@ -714,53 +756,24 @@ static void *__bfq_bic_change_cgroup(struct bfq_data *bfqd, struct bfq_io_cq *bic, struct bfq_group *bfqg) { - struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0); - struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1); struct bfq_entity *entity; + unsigned int act_idx; - if (async_bfqq) { - entity = &async_bfqq->entity; - - if (entity->sched_data != &bfqg->sched_data) { - bic_set_bfqq(bic, NULL, 0); - bfq_release_process_ref(bfqd, async_bfqq); - } - } + for (act_idx = 0; act_idx < bfqd->num_actuators; act_idx++) { + struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0, act_idx); + struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1, act_idx); - if (sync_bfqq) { - if (!sync_bfqq->new_bfqq && !bfq_bfqq_coop(sync_bfqq)) { - /* We are the only user of this bfqq, just move it */ - if (sync_bfqq->entity.sched_data != &bfqg->sched_data) - bfq_bfqq_move(bfqd, sync_bfqq, bfqg); - } else { - struct bfq_queue *bfqq; + if (async_bfqq) { + entity = &async_bfqq->entity; - /* - * The queue was merged to a different queue. Check - * that the merge chain still belongs to the same - * cgroup. - */ - for (bfqq = sync_bfqq; bfqq; bfqq = bfqq->new_bfqq) - if (bfqq->entity.sched_data != - &bfqg->sched_data) - break; - if (bfqq) { - /* - * Some queue changed cgroup so the merge is - * not valid anymore. We cannot easily just - * cancel the merge (by clearing new_bfqq) as - * there may be other processes using this - * queue and holding refs to all queues below - * sync_bfqq->new_bfqq. Similarly if the merge - * already happened, we need to detach from - * bfqq now so that we cannot merge bio to a - * request from the old cgroup. - */ - bfq_put_cooperator(sync_bfqq); - bfq_release_process_ref(bfqd, sync_bfqq); - bic_set_bfqq(bic, NULL, 1); + if (entity->sched_data != &bfqg->sched_data) { + bic_set_bfqq(bic, NULL, 0, act_idx); + bfq_release_process_ref(bfqd, async_bfqq); } } + + if (sync_bfqq) + bfq_sync_bfqq_move(bfqd, sync_bfqq, bic, bfqg, act_idx); } return bfqg; diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 7ea427817f7f..99c01e184f1d 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -377,14 +377,19 @@ static const unsigned long bfq_late_stable_merging = 600; #define RQ_BIC(rq) ((struct bfq_io_cq *)((rq)->elv.priv[0])) #define RQ_BFQQ(rq) ((rq)->elv.priv[1]) -struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync) +struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, + bool is_sync, + unsigned int actuator_idx) { - return bic->bfqq[is_sync]; + return bic->bfqq[is_sync][actuator_idx]; } static void bfq_put_stable_ref(struct bfq_queue *bfqq); -void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, bool is_sync) +void bic_set_bfqq(struct bfq_io_cq *bic, + struct bfq_queue *bfqq, + bool is_sync, + unsigned int actuator_idx) { /* * If bfqq != NULL, then a non-stable queue merge between @@ -399,7 +404,7 @@ void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, bool is_sync) * we cancel the stable merge if * bic->stable_merge_bfqq == bfqq. */ - bic->bfqq[is_sync] = bfqq; + bic->bfqq[is_sync][actuator_idx] = bfqq; if (bfqq && bic->stable_merge_bfqq == bfqq) { /* @@ -672,9 +677,9 @@ static void bfq_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data) { struct bfq_data *bfqd = data->q->elevator->elevator_data; struct bfq_io_cq *bic = bfq_bic_lookup(data->q); - struct bfq_queue *bfqq = bic ? bic_to_bfqq(bic, op_is_sync(opf)) : NULL; int depth; unsigned limit = data->q->nr_requests; + unsigned int act_idx; /* Sync reads have full depth available */ if (op_is_sync(opf) && !op_is_write(opf)) { @@ -684,14 +689,21 @@ static void bfq_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data) limit = (limit * depth) >> bfqd->full_depth_shift; } - /* - * Does queue (or any parent entity) exceed number of requests that - * should be available to it? Heavily limit depth so that it cannot - * consume more available requests and thus starve other entities. - */ - if (bfqq && bfqq_request_over_limit(bfqq, limit)) - depth = 1; + for (act_idx = 0; act_idx < bfqd->num_actuators; act_idx++) { + struct bfq_queue *bfqq = + bic ? bic_to_bfqq(bic, op_is_sync(opf), act_idx) : NULL; + /* + * Does queue (or any parent entity) exceed number of + * requests that should be available to it? Heavily + * limit depth so that it cannot consume more + * available requests and thus starve other entities. + */ + if (bfqq && bfqq_request_over_limit(bfqq, limit)) { + depth = 1; + break; + } + } bfq_log(bfqd, "[%s] wr_busy %d sync %d depth %u", __func__, bfqd->wr_busy_queues, op_is_sync(opf), depth); if (depth) @@ -2142,7 +2154,7 @@ static void bfq_check_waker(struct bfq_data *bfqd, struct bfq_queue *bfqq, * We reset waker detection logic also if too much time has passed * since the first detection. If wakeups are rare, pointless idling * doesn't hurt throughput that much. The condition below makes sure - * we do not uselessly idle blocking waker in more than 1/64 cases. + * we do not uselessly idle blocking waker in more than 1/64 cases. */ if (bfqd->last_completed_rq_bfqq != bfqq->tentative_waker_bfqq || @@ -2454,6 +2466,16 @@ static void bfq_remove_request(struct request_queue *q, } +/* get the index of the actuator that will serve bio */ +static unsigned int bfq_actuator_index(struct bfq_data *bfqd, struct bio *bio) +{ + /* + * Multi-actuator support not complete yet, so always return 0 + * for the moment. + */ + return 0; +} + static bool bfq_bio_merge(struct request_queue *q, struct bio *bio, unsigned int nr_segs) { @@ -2478,7 +2500,8 @@ static bool bfq_bio_merge(struct request_queue *q, struct bio *bio, */ bfq_bic_update_cgroup(bic, bio); - bfqd->bio_bfqq = bic_to_bfqq(bic, op_is_sync(bio->bi_opf)); + bfqd->bio_bfqq = bic_to_bfqq(bic, op_is_sync(bio->bi_opf), + bfq_actuator_index(bfqd, bio)); } else { bfqd->bio_bfqq = NULL; } @@ -3174,7 +3197,7 @@ bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic, /* * Merge queues (that is, let bic redirect its requests to new_bfqq) */ - bic_set_bfqq(bic, new_bfqq, 1); + bic_set_bfqq(bic, new_bfqq, 1, bfqq->actuator_idx); bfq_mark_bfqq_coop(new_bfqq); /* * new_bfqq now belongs to at least two bics (it is a shared queue): @@ -4808,11 +4831,12 @@ static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd) */ if (bfq_bfqq_wait_request(bfqq) || (bfqq->dispatched != 0 && bfq_better_to_idle(bfqq))) { + unsigned int act_idx = bfqq->actuator_idx; struct bfq_queue *async_bfqq = - bfqq->bic && bfqq->bic->bfqq[0] && - bfq_bfqq_busy(bfqq->bic->bfqq[0]) && - bfqq->bic->bfqq[0]->next_rq ? - bfqq->bic->bfqq[0] : NULL; + bfqq->bic && bfqq->bic->bfqq[0][act_idx] && + bfq_bfqq_busy(bfqq->bic->bfqq[0][act_idx]) && + bfqq->bic->bfqq[0][act_idx]->next_rq ? + bfqq->bic->bfqq[0][act_idx] : NULL; struct bfq_queue *blocked_bfqq = !hlist_empty(&bfqq->woken_list) ? container_of(bfqq->woken_list.first, @@ -4904,7 +4928,7 @@ static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd) icq_to_bic(async_bfqq->next_rq->elv.icq) == bfqq->bic && bfq_serv_to_charge(async_bfqq->next_rq, async_bfqq) <= bfq_bfqq_budget_left(async_bfqq)) - bfqq = bfqq->bic->bfqq[0]; + bfqq = bfqq->bic->bfqq[0][act_idx]; else if (bfqq->waker_bfqq && bfq_bfqq_busy(bfqq->waker_bfqq) && bfqq->waker_bfqq->next_rq && @@ -5365,49 +5389,47 @@ static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) bfq_release_process_ref(bfqd, bfqq); } -static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync) +static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, + bool is_sync, + unsigned int actuator_idx) { - struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync); + struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync, actuator_idx); struct bfq_data *bfqd; if (bfqq) bfqd = bfqq->bfqd; /* NULL if scheduler already exited */ if (bfqq && bfqd) { - unsigned long flags; - - spin_lock_irqsave(&bfqd->lock, flags); bfqq->bic = NULL; bfq_exit_bfqq(bfqd, bfqq); - bic_set_bfqq(bic, NULL, is_sync); - spin_unlock_irqrestore(&bfqd->lock, flags); + bic_set_bfqq(bic, NULL, is_sync, actuator_idx); } } static void bfq_exit_icq(struct io_cq *icq) { struct bfq_io_cq *bic = icq_to_bic(icq); + struct bfq_data *bfqd = bic_to_bfqd(bic); + unsigned long flags; + unsigned int act_idx; - if (bic->stable_merge_bfqq) { - struct bfq_data *bfqd = bic->stable_merge_bfqq->bfqd; - - /* - * bfqd is NULL if scheduler already exited, and in - * that case this is the last time bfqq is accessed. - */ - if (bfqd) { - unsigned long flags; + /* + * bfqd is NULL if scheduler already exited, and in that case + * this is the last time these queues are accessed. + */ + if (bfqd) + spin_lock_irqsave(&bfqd->lock, flags); - spin_lock_irqsave(&bfqd->lock, flags); - bfq_put_stable_ref(bic->stable_merge_bfqq); - spin_unlock_irqrestore(&bfqd->lock, flags); - } else { + for (act_idx = 0; act_idx < bfqd->num_actuators; act_idx++) { + if (bic->stable_merge_bfqq) bfq_put_stable_ref(bic->stable_merge_bfqq); - } + + bfq_exit_icq_bfqq(bic, true, act_idx); + bfq_exit_icq_bfqq(bic, false, act_idx); } - bfq_exit_icq_bfqq(bic, true); - bfq_exit_icq_bfqq(bic, false); + if (bfqd) + spin_unlock_irqrestore(&bfqd->lock, flags); } /* @@ -5484,23 +5506,25 @@ static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio) bic->ioprio = ioprio; - bfqq = bic_to_bfqq(bic, false); + bfqq = bic_to_bfqq(bic, false, bfq_actuator_index(bfqd, bio)); if (bfqq) { bfq_release_process_ref(bfqd, bfqq); bfqq = bfq_get_queue(bfqd, bio, false, bic, true); - bic_set_bfqq(bic, bfqq, false); + bic_set_bfqq(bic, bfqq, false, bfq_actuator_index(bfqd, bio)); } - bfqq = bic_to_bfqq(bic, true); + bfqq = bic_to_bfqq(bic, true, bfq_actuator_index(bfqd, bio)); if (bfqq) bfq_set_next_ioprio_data(bfqq, bic); } static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, - struct bfq_io_cq *bic, pid_t pid, int is_sync) + struct bfq_io_cq *bic, pid_t pid, int is_sync, + unsigned int act_idx) { u64 now_ns = ktime_get_ns(); + bfqq->actuator_idx = act_idx; RB_CLEAR_NODE(&bfqq->entity.rb_node); INIT_LIST_HEAD(&bfqq->fifo); INIT_HLIST_NODE(&bfqq->burst_list_node); @@ -5739,6 +5763,7 @@ static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, struct bfq_group *bfqg; bfqg = bfq_bio_bfqg(bfqd, bio); + if (!is_sync) { async_bfqq = bfq_async_queue_prio(bfqd, bfqg, ioprio_class, ioprio); @@ -5753,7 +5778,7 @@ static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, if (bfqq) { bfq_init_bfqq(bfqd, bfqq, bic, current->pid, - is_sync); + is_sync, bfq_actuator_index(bfqd, bio)); bfq_init_entity(&bfqq->entity, bfqg); bfq_log_bfqq(bfqd, bfqq, "allocated"); } else { @@ -6068,7 +6093,8 @@ static bool __bfq_insert_request(struct bfq_data *bfqd, struct request *rq) * then complete the merge and redirect it to * new_bfqq. */ - if (bic_to_bfqq(RQ_BIC(rq), 1) == bfqq) + if (bic_to_bfqq(RQ_BIC(rq), 1, + bfq_actuator_index(bfqd, rq->bio)) == bfqq) bfq_merge_bfqqs(bfqd, RQ_BIC(rq), bfqq, new_bfqq); @@ -6622,7 +6648,7 @@ bfq_split_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq) return bfqq; } - bic_set_bfqq(bic, NULL, 1); + bic_set_bfqq(bic, NULL, 1, bfqq->actuator_idx); bfq_put_cooperator(bfqq); @@ -6636,7 +6662,8 @@ static struct bfq_queue *bfq_get_bfqq_handle_split(struct bfq_data *bfqd, bool split, bool is_sync, bool *new_queue) { - struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync); + unsigned int act_idx = bfq_actuator_index(bfqd, bio); + struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync, act_idx); if (likely(bfqq && bfqq != &bfqd->oom_bfqq)) return bfqq; @@ -6648,7 +6675,7 @@ static struct bfq_queue *bfq_get_bfqq_handle_split(struct bfq_data *bfqd, bfq_put_queue(bfqq); bfqq = bfq_get_queue(bfqd, bio, is_sync, bic, split); - bic_set_bfqq(bic, bfqq, is_sync); + bic_set_bfqq(bic, bfqq, is_sync, act_idx); if (split && is_sync) { if ((bic->was_in_burst_list && bfqd->large_burst) || bic->saved_in_large_burst) @@ -7090,8 +7117,10 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e) * Our fallback bfqq if bfq_find_alloc_queue() runs into OOM issues. * Grab a permanent reference to it, so that the normal code flow * will not attempt to free it. + * Set zero as actuator index: we will pretend that + * all I/O requests are for the same actuator. */ - bfq_init_bfqq(bfqd, &bfqd->oom_bfqq, NULL, 1, 0); + bfq_init_bfqq(bfqd, &bfqd->oom_bfqq, NULL, 1, 0, 0); bfqd->oom_bfqq.ref++; bfqd->oom_bfqq.new_ioprio = BFQ_DEFAULT_QUEUE_IOPRIO; bfqd->oom_bfqq.new_ioprio_class = IOPRIO_CLASS_BE; @@ -7110,6 +7139,12 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e) bfqd->queue = q; + /* + * Multi-actuator support not complete yet, default to single + * actuator for the moment. + */ + bfqd->num_actuators = 1; + INIT_LIST_HEAD(&bfqd->dispatch); hrtimer_init(&bfqd->idle_slice_timer, CLOCK_MONOTONIC, diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 64ee618064ba..d98e31be447f 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -33,6 +33,14 @@ */ #define BFQ_SOFTRT_WEIGHT_FACTOR 100 +/* + * Maximum number of actuators supported. This constant is used simply + * to define the size of the static array that will contain + * per-actuator data. The current value is hopefully a good upper + * bound to the possible number of actuators of any actual drive. + */ +#define BFQ_MAX_ACTUATORS 32 + struct bfq_entity; /** @@ -225,12 +233,14 @@ struct bfq_ttime { * struct bfq_queue - leaf schedulable entity. * * A bfq_queue is a leaf request queue; it can be associated with an - * io_context or more, if it is async or shared between cooperating - * processes. @cgroup holds a reference to the cgroup, to be sure that it - * does not disappear while a bfqq still references it (mostly to avoid - * races between request issuing and task migration followed by cgroup - * destruction). - * All the fields are protected by the queue lock of the containing bfqd. + * io_context or more, if it is async or shared between cooperating + * processes. Besides, it contains I/O requests for only one actuator + * (an io_context is associated with a different bfq_queue for each + * actuator it generates I/O for). @cgroup holds a reference to the + * cgroup, to be sure that it does not disappear while a bfqq still + * references it (mostly to avoid races between request issuing and + * task migration followed by cgroup destruction). All the fields are + * protected by the queue lock of the containing bfqd. */ struct bfq_queue { /* reference counter */ @@ -399,6 +409,9 @@ struct bfq_queue { * the woken queues when this queue exits. */ struct hlist_head woken_list; + + /* index of the actuator this queue is associated with */ + unsigned int actuator_idx; }; /** @@ -407,8 +420,17 @@ struct bfq_queue { struct bfq_io_cq { /* associated io_cq structure */ struct io_cq icq; /* must be the first member */ - /* array of two process queues, the sync and the async */ - struct bfq_queue *bfqq[2]; + /* + * Matrix of associated process queues: first row for async + * queues, second row sync queues. Each row contains one + * column for each actuator. An I/O request generated by the + * process is inserted into the queue pointed by bfqq[i][j] if + * the request is to be served by the j-th actuator of the + * drive, where i==0 or i==1, depending on whether the request + * is async or sync. So there is a distinct queue for each + * actuator. + */ + struct bfq_queue *bfqq[2][BFQ_MAX_ACTUATORS]; /* per (request_queue, blkcg) ioprio */ int ioprio; #ifdef CONFIG_BFQ_GROUP_IOSCHED @@ -772,6 +794,13 @@ struct bfq_data { */ unsigned int word_depths[2][2]; unsigned int full_depth_shift; + + /* + * Number of independent actuators. This is equal to 1 in + * case of single-actuator drives. + */ + unsigned int num_actuators; + }; enum bfqq_state_flags { @@ -968,8 +997,10 @@ struct bfq_group { extern const int bfq_timeout; -struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync); -void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, bool is_sync); +struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync, + unsigned int actuator_idx); +void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq, bool is_sync, + unsigned int actuator_idx); struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic); void bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq); void bfq_weights_tree_add(struct bfq_data *bfqd, struct bfq_queue *bfqq, From patchwork Thu Oct 20 15:26:37 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Valente X-Patchwork-Id: 6255 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4242:0:0:0:0:0 with SMTP id s2csp173314wrr; Thu, 20 Oct 2022 08:28:15 -0700 (PDT) X-Google-Smtp-Source: AMsMyM5JFizp9GYuWRWjdELfSK2kZagxxpRWCSEbICe/5LBhJajF387APkOvv+Yw19HiPpCvsbOG X-Received: by 2002:a17:907:9627:b0:78d:a7d8:9407 with SMTP id gb39-20020a170907962700b0078da7d89407mr11330003ejc.675.1666279694941; Thu, 20 Oct 2022 08:28:14 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1666279694; cv=none; d=google.com; s=arc-20160816; b=vl7zK80ucO/D84FPgZxSkqEmI+Pbgj01UxFUs9cT/YLbQil8x6Hd2RiRYrds7r5Ck3 4bz9R6Vq6pSDlP02eOVIsC0xswWpo3qIca4D5ORIyqUaYRa72GLjOH19ra1UUYNabMFI ANcWiXx7MPGGpZVWAAytCGgcTlKw1Spo0pciJGoa2akcxtHwDxvpBPhhk93Qiv67FkJZ O/2ThaWLz6zXpxxRb/Q3GcWZAfRag/2lrqzgqxeAG9o6tQZyqNIIHXrWTFAsxbV4VBQY DVb3+N/sSBpRRrdb1KK05mj/Ep8tAQrFDuAkMPZeOnf5KcXNxpIOkP9WspVKl1UckBGO uUvw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=FX2t3qf8BSgHA3maXGdOtEQ+vTybs9QvWGjlXMhif64=; b=gr0SlVM6pnSGXPg8YqdFOPL1m7EZNZXA2htee7FQXMjKvOXcD8DByqJipuJX+39Bl+ g+MwT9kWP9lFGxvO+SgfVSX7yqEeAEUnbHVOBZ00tw0N1GYCZOgYZjDsZ2XBCkhP5BDJ TEgciILmzyXiWKVtQCJgRk7+WJsKIQpB2eOZeJYAS8nIxccNQY1OQN7RnukJxcYo+KJG VT8685FiNuf3JTUnwQhaDzqwyf477dzXJKVV8HDuUc4kEF+edXJ5eK0hiZvLuvLTix/7 GuUmfc2vFORb/tHzdUV5fQhysMubwPwD6yfW4EjkmajC41F8cR2PRzTAMOQG4bdot9R5 FZQg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=J+8zRhNj; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: from out1.vger.email (out1.vger.email. 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[2.35.55.161]) by smtp.gmail.com with ESMTPSA id l10-20020a1ced0a000000b003c409244bb0sm134337wmh.6.2022.10.20.08.26.54 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Oct 2022 08:26:55 -0700 (PDT) From: Paolo Valente To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, glen.valante@linaro.org, arie.vanderhoeven@seagate.com, rory.c.chen@seagate.com, Paolo Valente Subject: [PATCH V4 2/8] block, bfq: forbid stable merging of queues associated with different actuators Date: Thu, 20 Oct 2022 17:26:37 +0200 Message-Id: <20221020152643.21199-3-paolo.valente@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20221020152643.21199-1-paolo.valente@linaro.org> References: <20221020152643.21199-1-paolo.valente@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747220897375080241?= X-GMAIL-MSGID: =?utf-8?q?1747220897375080241?= If queues associated with different actuators are merged, then control is lost on each actuator. Therefore some actuator may be underutilized, and throughput may decrease. This problem cannot occur with basic queue merging, because the latter is triggered by spatial locality, and sectors for different actuators are not close to each other. Yet it may happen with stable merging. To address this issue, this commit prevents stable merging from occurring among queues associated with different actuators. Signed-off-by: Paolo Valente --- block/bfq-iosched.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 99c01e184f1d..57de6a6a7f06 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -5693,9 +5693,13 @@ static struct bfq_queue *bfq_do_or_sched_stable_merge(struct bfq_data *bfqd, * it has been set already, but too long ago, then move it * forward to bfqq. Finally, move also if bfqq belongs to a * different group than last_bfqq_created, or if bfqq has a - * different ioprio or ioprio_class. If none of these - * conditions holds true, then try an early stable merge or - * schedule a delayed stable merge. + * different ioprio, ioprio_class or actuator_idx. If none of + * these conditions holds true, then try an early stable merge + * or schedule a delayed stable merge. As for the condition on + * actuator_idx, the reason is that, if queues associated with + * different actuators are merged, then control is lost on + * each actuator. Therefore some actuator may be + * underutilized, and throughput may decrease. * * A delayed merge is scheduled (instead of performing an * early merge), in case bfqq might soon prove to be more @@ -5713,7 +5717,8 @@ static struct bfq_queue *bfq_do_or_sched_stable_merge(struct bfq_data *bfqd, bfqq->creation_time) || bfqq->entity.parent != last_bfqq_created->entity.parent || bfqq->ioprio != last_bfqq_created->ioprio || - bfqq->ioprio_class != last_bfqq_created->ioprio_class) + bfqq->ioprio_class != last_bfqq_created->ioprio_class || + bfqq->actuator_idx != last_bfqq_created->actuator_idx) *source_bfqq = bfqq; else if (time_after_eq(last_bfqq_created->creation_time + bfqd->bfq_burst_interval, From patchwork Thu Oct 20 15:26:38 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Valente X-Patchwork-Id: 6257 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4242:0:0:0:0:0 with SMTP id s2csp173556wrr; Thu, 20 Oct 2022 08:28:43 -0700 (PDT) X-Google-Smtp-Source: AMsMyM7BjUoNrozwE8lvjrE9YkDp9o6O/vyCG91Nz1/G71IDFgc9/UMzaG7FaDZQ9odmTRU+861p X-Received: by 2002:a05:6402:1690:b0:45f:d702:9919 with SMTP id a16-20020a056402169000b0045fd7029919mr4290390edv.127.1666279723279; Thu, 20 Oct 2022 08:28:43 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1666279723; cv=none; d=google.com; s=arc-20160816; b=KdFSq/o2/csELCiYLV9XwoZi7LKb0jjIDzHNpor9X4xCo635VMHrVwMRGSQnd2fiuD eTHUtrquL2J4UxTYbAn7lay9E9ZGOU6haTk1HP1yOu2xoDYbPq7CJ/r4+Fkug+LNd4Kz SWAA5MoWhMMuf/htQ1rmcVG+XAAkSUsXM/u5yw3hivGa5kgzQLyH6iC8sW3DZ38DOT/0 T5EJxUqB0wsx6LceTsD5Lanm2YdX7kWq6ojiChfUCaxU0Q66WDiTaHRc9My5tVtUtTGH vQ/JjFuQrdRPGhc99uG3z6HrYKGh3ozbW7UAUzJcHbrXS6ITMncFm9VihIuIrd2uf6wv CqWQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=pOn+31mximXGw88FTtnbU7DllPEek+g8kJecNxz5KjE=; b=NW9AKIlqW+t27VqxHokuV+FdYjwuZpIQVAV+OlbKB+7WbUAXrE8+5BcvAKPgoon+mC xPQkdCjZ4g1NAQBn4U8Qz0RBTKuUBOA3NJnUVFyVCQelWgifyxFzyGbWKA9kZKH2YiMX FAixCyY3WisKNspwFC0sjq9F9XBXoiofypHtqDk55SBDlWF2bf3epY/iUSKOaCQWY69Z h5R3cexiiympOckNn03utARgGLzY60gTGk7DvzkkUVm5JF1aUpshatTLSNsCHYjH61OP /Dao0h0/yhYQRFe6AF5DUtK/BxNtLmzGZE7DkLdAHgHeoI+WBaRajg9g2KiEGrpbZjJ1 uoXQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=VusxOHdN; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: from out1.vger.email (out1.vger.email. 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[2.35.55.161]) by smtp.gmail.com with ESMTPSA id l10-20020a1ced0a000000b003c409244bb0sm134337wmh.6.2022.10.20.08.26.55 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Oct 2022 08:26:56 -0700 (PDT) From: Paolo Valente To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, glen.valante@linaro.org, arie.vanderhoeven@seagate.com, rory.c.chen@seagate.com, Paolo Valente , Damien Le Moal , Gianmarco Lusvardi , Giulio Barabino , Emiliano Maccaferri Subject: [PATCH V4 3/8] block, bfq: move io_cq-persistent bfqq data into a dedicated struct Date: Thu, 20 Oct 2022 17:26:38 +0200 Message-Id: <20221020152643.21199-4-paolo.valente@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20221020152643.21199-1-paolo.valente@linaro.org> References: <20221020152643.21199-1-paolo.valente@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747220927234360820?= X-GMAIL-MSGID: =?utf-8?q?1747220927234360820?= With a multi-actuator drive, a process may get associated with multiple bfq_queues: one queue for each of the N actuators. So, the bfq_io_cq data structure must be able to accommodate its per-queue persistent information for N queues. Currently it stores this information for just one queue, in several scalar fields. This is a preparatory commit for moving to accommodating persistent information for N queues. In particular, this commit packs all the above scalar fields into a single data structure. Then there is now only one fieldi, in bfq_io_cq, that stores all the above information. This scalar field will then be turned into an array by a following commit. Suggested-by: Damien Le Moal Signed-off-by: Gianmarco Lusvardi Signed-off-by: Giulio Barabino Signed-off-by: Emiliano Maccaferri Signed-off-by: Paolo Valente --- block/bfq-iosched.c | 118 +++++++++++++++++++++++--------------------- block/bfq-iosched.h | 52 +++++++++++-------- 2 files changed, 94 insertions(+), 76 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 57de6a6a7f06..d2bd94ea2e95 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -406,7 +406,7 @@ void bic_set_bfqq(struct bfq_io_cq *bic, */ bic->bfqq[is_sync][actuator_idx] = bfqq; - if (bfqq && bic->stable_merge_bfqq == bfqq) { + if (bfqq && bic->bfqq_data->stable_merge_bfqq == bfqq) { /* * Actually, these same instructions are executed also * in bfq_setup_cooperator, in case of abort or actual @@ -415,9 +415,9 @@ void bic_set_bfqq(struct bfq_io_cq *bic, * did so, we would nest even more complexity in this * function. */ - bfq_put_stable_ref(bic->stable_merge_bfqq); + bfq_put_stable_ref(bic->bfqq_data->stable_merge_bfqq); - bic->stable_merge_bfqq = NULL; + bic->bfqq_data->stable_merge_bfqq = NULL; } } @@ -1177,35 +1177,36 @@ bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd, unsigned int old_wr_coeff = 1; bool busy = bfq_already_existing && bfq_bfqq_busy(bfqq); - if (bic->saved_has_short_ttime) + if (bic->bfqq_data->saved_has_short_ttime) bfq_mark_bfqq_has_short_ttime(bfqq); else bfq_clear_bfqq_has_short_ttime(bfqq); - if (bic->saved_IO_bound) + if (bic->bfqq_data->saved_IO_bound) bfq_mark_bfqq_IO_bound(bfqq); else bfq_clear_bfqq_IO_bound(bfqq); - bfqq->last_serv_time_ns = bic->saved_last_serv_time_ns; - bfqq->inject_limit = bic->saved_inject_limit; - bfqq->decrease_time_jif = bic->saved_decrease_time_jif; + bfqq->last_serv_time_ns = bic->bfqq_data->saved_last_serv_time_ns; + bfqq->inject_limit = bic->bfqq_data->saved_inject_limit; + bfqq->decrease_time_jif = bic->bfqq_data->saved_decrease_time_jif; - bfqq->entity.new_weight = bic->saved_weight; - bfqq->ttime = bic->saved_ttime; - bfqq->io_start_time = bic->saved_io_start_time; - bfqq->tot_idle_time = bic->saved_tot_idle_time; + bfqq->entity.new_weight = bic->bfqq_data->saved_weight; + bfqq->ttime = bic->bfqq_data->saved_ttime; + bfqq->io_start_time = bic->bfqq_data->saved_io_start_time; + bfqq->tot_idle_time = bic->bfqq_data->saved_tot_idle_time; /* * Restore weight coefficient only if low_latency is on */ if (bfqd->low_latency) { old_wr_coeff = bfqq->wr_coeff; - bfqq->wr_coeff = bic->saved_wr_coeff; + bfqq->wr_coeff = bic->bfqq_data->saved_wr_coeff; } - bfqq->service_from_wr = bic->saved_service_from_wr; - bfqq->wr_start_at_switch_to_srt = bic->saved_wr_start_at_switch_to_srt; - bfqq->last_wr_start_finish = bic->saved_last_wr_start_finish; - bfqq->wr_cur_max_time = bic->saved_wr_cur_max_time; + bfqq->service_from_wr = bic->bfqq_data->saved_service_from_wr; + bfqq->wr_start_at_switch_to_srt = + bic->bfqq_data->saved_wr_start_at_switch_to_srt; + bfqq->last_wr_start_finish = bic->bfqq_data->saved_last_wr_start_finish; + bfqq->wr_cur_max_time = bic->bfqq_data->saved_wr_cur_max_time; if (bfqq->wr_coeff > 1 && (bfq_bfqq_in_large_burst(bfqq) || time_is_before_jiffies(bfqq->last_wr_start_finish + @@ -1878,7 +1879,7 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, wr_or_deserves_wr = bfqd->low_latency && (bfqq->wr_coeff > 1 || (bfq_bfqq_sync(bfqq) && - (bfqq->bic || RQ_BIC(rq)->stably_merged) && + (bfqq->bic || RQ_BIC(rq)->bfqq_data->stably_merged) && (*interactive || soft_rt))); /* @@ -2923,21 +2924,21 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, * stable merging) also if bic is associated with a * sync queue, but this bfqq is async */ - if (bfq_bfqq_sync(bfqq) && bic->stable_merge_bfqq && + if (bfq_bfqq_sync(bfqq) && bic->bfqq_data->stable_merge_bfqq && !bfq_bfqq_just_created(bfqq) && time_is_before_jiffies(bfqq->split_time + msecs_to_jiffies(bfq_late_stable_merging)) && time_is_before_jiffies(bfqq->creation_time + msecs_to_jiffies(bfq_late_stable_merging))) { struct bfq_queue *stable_merge_bfqq = - bic->stable_merge_bfqq; + bic->bfqq_data->stable_merge_bfqq; int proc_ref = min(bfqq_process_refs(bfqq), bfqq_process_refs(stable_merge_bfqq)); /* deschedule stable merge, because done or aborted here */ bfq_put_stable_ref(stable_merge_bfqq); - bic->stable_merge_bfqq = NULL; + bic->bfqq_data->stable_merge_bfqq = NULL; if (!idling_boosts_thr_without_issues(bfqd, bfqq) && proc_ref > 0) { @@ -2946,10 +2947,10 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, bfq_setup_merge(bfqq, stable_merge_bfqq); if (new_bfqq) { - bic->stably_merged = true; + bic->bfqq_data->stably_merged = true; if (new_bfqq->bic) - new_bfqq->bic->stably_merged = - true; + new_bfqq->bic->bfqq_data->stably_merged = + true; } return new_bfqq; } else @@ -3057,18 +3058,21 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq) if (!bic) return; - bic->saved_last_serv_time_ns = bfqq->last_serv_time_ns; - bic->saved_inject_limit = bfqq->inject_limit; - bic->saved_decrease_time_jif = bfqq->decrease_time_jif; - - bic->saved_weight = bfqq->entity.orig_weight; - bic->saved_ttime = bfqq->ttime; - bic->saved_has_short_ttime = bfq_bfqq_has_short_ttime(bfqq); - bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq); - bic->saved_io_start_time = bfqq->io_start_time; - bic->saved_tot_idle_time = bfqq->tot_idle_time; - bic->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq); - bic->was_in_burst_list = !hlist_unhashed(&bfqq->burst_list_node); + bic->bfqq_data->saved_last_serv_time_ns = bfqq->last_serv_time_ns; + bic->bfqq_data->saved_inject_limit = bfqq->inject_limit; + bic->bfqq_data->saved_decrease_time_jif = bfqq->decrease_time_jif; + + bic->bfqq_data->saved_weight = bfqq->entity.orig_weight; + bic->bfqq_data->saved_ttime = bfqq->ttime; + bic->bfqq_data->saved_has_short_ttime = + bfq_bfqq_has_short_ttime(bfqq); + bic->bfqq_data->saved_IO_bound = bfq_bfqq_IO_bound(bfqq); + bic->bfqq_data->saved_io_start_time = bfqq->io_start_time; + bic->bfqq_data->saved_tot_idle_time = bfqq->tot_idle_time; + bic->bfqq_data->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq); + bic->bfqq_data->was_in_burst_list = + !hlist_unhashed(&bfqq->burst_list_node); + if (unlikely(bfq_bfqq_just_created(bfqq) && !bfq_bfqq_in_large_burst(bfqq) && bfqq->bfqd->low_latency)) { @@ -3081,17 +3085,21 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq) * to bfqq, so that to avoid that bfqq unjustly fails * to enjoy weight raising if split soon. */ - bic->saved_wr_coeff = bfqq->bfqd->bfq_wr_coeff; - bic->saved_wr_start_at_switch_to_srt = bfq_smallest_from_now(); - bic->saved_wr_cur_max_time = bfq_wr_duration(bfqq->bfqd); - bic->saved_last_wr_start_finish = jiffies; + bic->bfqq_data->saved_wr_coeff = bfqq->bfqd->bfq_wr_coeff; + bic->bfqq_data->saved_wr_start_at_switch_to_srt = + bfq_smallest_from_now(); + bic->bfqq_data->saved_wr_cur_max_time = + bfq_wr_duration(bfqq->bfqd); + bic->bfqq_data->saved_last_wr_start_finish = jiffies; } else { - bic->saved_wr_coeff = bfqq->wr_coeff; - bic->saved_wr_start_at_switch_to_srt = + bic->bfqq_data->saved_wr_coeff = bfqq->wr_coeff; + bic->bfqq_data->saved_wr_start_at_switch_to_srt = bfqq->wr_start_at_switch_to_srt; - bic->saved_service_from_wr = bfqq->service_from_wr; - bic->saved_last_wr_start_finish = bfqq->last_wr_start_finish; - bic->saved_wr_cur_max_time = bfqq->wr_cur_max_time; + bic->bfqq_data->saved_service_from_wr = + bfqq->service_from_wr; + bic->bfqq_data->saved_last_wr_start_finish = + bfqq->last_wr_start_finish; + bic->bfqq_data->saved_wr_cur_max_time = bfqq->wr_cur_max_time; } } @@ -5421,8 +5429,8 @@ static void bfq_exit_icq(struct io_cq *icq) spin_lock_irqsave(&bfqd->lock, flags); for (act_idx = 0; act_idx < bfqd->num_actuators; act_idx++) { - if (bic->stable_merge_bfqq) - bfq_put_stable_ref(bic->stable_merge_bfqq); + if (bic->bfqq_data->stable_merge_bfqq) + bfq_put_stable_ref(bic->bfqq_data->stable_merge_bfqq); bfq_exit_icq_bfqq(bic, true, act_idx); bfq_exit_icq_bfqq(bic, false, act_idx); @@ -5617,8 +5625,8 @@ bfq_do_early_stable_merge(struct bfq_data *bfqd, struct bfq_queue *bfqq, return bfqq; if (new_bfqq->bic) - new_bfqq->bic->stably_merged = true; - bic->stably_merged = true; + new_bfqq->bic->bfqq_data->stably_merged = true; + bic->bfqq_data->stably_merged = true; /* * Reusing merge functions. This implies that @@ -5748,7 +5756,7 @@ static struct bfq_queue *bfq_do_or_sched_stable_merge(struct bfq_data *bfqd, /* * Record the bfqq to merge to. */ - bic->stable_merge_bfqq = last_bfqq_created; + bic->bfqq_data->stable_merge_bfqq = last_bfqq_created; } } @@ -6682,12 +6690,12 @@ static struct bfq_queue *bfq_get_bfqq_handle_split(struct bfq_data *bfqd, bic_set_bfqq(bic, bfqq, is_sync, act_idx); if (split && is_sync) { - if ((bic->was_in_burst_list && bfqd->large_burst) || - bic->saved_in_large_burst) + if ((bic->bfqq_data->was_in_burst_list && bfqd->large_burst) || + bic->bfqq_data->saved_in_large_burst) bfq_mark_bfqq_in_large_burst(bfqq); else { bfq_clear_bfqq_in_large_burst(bfqq); - if (bic->was_in_burst_list) + if (bic->bfqq_data->was_in_burst_list) /* * If bfqq was in the current * burst list before being @@ -6802,12 +6810,12 @@ static struct bfq_queue *bfq_init_rq(struct request *rq) if (likely(!new_queue)) { /* If the queue was seeky for too long, break it apart. */ if (bfq_bfqq_coop(bfqq) && bfq_bfqq_split_coop(bfqq) && - !bic->stably_merged) { + !bic->bfqq_data->stably_merged) { struct bfq_queue *old_bfqq = bfqq; /* Update bic before losing reference to bfqq */ if (bfq_bfqq_in_large_burst(bfqq)) - bic->saved_in_large_burst = true; + bic->bfqq_data->saved_in_large_burst = true; bfqq = bfq_split_bfqq(bic, bfqq); split = true; diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index d98e31be447f..6bc7bed97956 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -415,27 +415,9 @@ struct bfq_queue { }; /** - * struct bfq_io_cq - per (request_queue, io_context) structure. - */ -struct bfq_io_cq { - /* associated io_cq structure */ - struct io_cq icq; /* must be the first member */ - /* - * Matrix of associated process queues: first row for async - * queues, second row sync queues. Each row contains one - * column for each actuator. An I/O request generated by the - * process is inserted into the queue pointed by bfqq[i][j] if - * the request is to be served by the j-th actuator of the - * drive, where i==0 or i==1, depending on whether the request - * is async or sync. So there is a distinct queue for each - * actuator. - */ - struct bfq_queue *bfqq[2][BFQ_MAX_ACTUATORS]; - /* per (request_queue, blkcg) ioprio */ - int ioprio; -#ifdef CONFIG_BFQ_GROUP_IOSCHED - uint64_t blkcg_serial_nr; /* the current blkcg serial */ -#endif +* struct bfq_data - bfqq data unique and persistent for associated bfq_io_cq +*/ +struct bfq_iocq_bfqq_data { /* * Snapshot of the has_short_time flag before merging; taken * to remember its value while the queue is merged, so as to @@ -490,6 +472,34 @@ struct bfq_io_cq { struct bfq_queue *stable_merge_bfqq; bool stably_merged; /* non splittable if true */ +}; + +/** + * struct bfq_io_cq - per (request_queue, io_context) structure. + */ +struct bfq_io_cq { + /* associated io_cq structure */ + struct io_cq icq; /* must be the first member */ + /* + * Matrix of associated process queues: first row for async + * queues, second row sync queues. Each row contains one + * column for each actuator. An I/O request generated by the + * process is inserted into the queue pointed by bfqq[i][j] if + * the request is to be served by the j-th actuator of the + * drive, where i==0 or i==1, depending on whether the request + * is async or sync. So there is a distinct queue for each + * actuator. + */ + struct bfq_queue *bfqq[2][BFQ_MAX_ACTUATORS]; + /* per (request_queue, blkcg) ioprio */ + int ioprio; +#ifdef CONFIG_BFQ_GROUP_IOSCHED + uint64_t blkcg_serial_nr; /* the current blkcg serial */ +#endif + + /* persistent data for associated synchronous process queue */ + struct bfq_iocq_bfqq_data *bfqq_data; + unsigned int requests; /* Number of requests this process has in flight */ }; From patchwork Thu Oct 20 15:26:39 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Valente X-Patchwork-Id: 6256 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4242:0:0:0:0:0 with SMTP id s2csp173402wrr; Thu, 20 Oct 2022 08:28:22 -0700 (PDT) X-Google-Smtp-Source: AMsMyM5W7U+Wvzj4n41D78sEhidX0yEaAX8ZMYZ7SXAxMiMadasm9RFZL/8Yce7f+OebC1UBxKTr X-Received: by 2002:a17:907:720b:b0:78e:c0e:a434 with SMTP id dr11-20020a170907720b00b0078e0c0ea434mr11490886ejc.741.1666279701861; Thu, 20 Oct 2022 08:28:21 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1666279701; cv=none; d=google.com; s=arc-20160816; b=pUffhVSeZcPK+q3tKxBO6pB72Ah63wrAv6iC1rvihYtSR2c4C4RRuGHORvWZRznv+R FGh/UIeRMzQkx2S6FEmsaMLwobNFqZME3Jf4Qy0lU1ZuCvC5+q5rIB4KjgP/0yxrhiSS UgnLiNqZZUt0e9X88+RSPpYJpYS1YfmUxxlrvKuvdnROuWpRz41K5ylCzwtoPyWaFYnh CqF5OmzISYL6BD/Zt/LeAgAjRKQvZmtrihNPVdW69TkmFJpOG3SF/aF0db6YhS/TzKgw 82K1USxdNf8sr+NmmCkOPR+CSwZN2GjJP/OBSXQMtSnMzrfno1sj1kbS1JBneyHtbOTv fDPQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=QEuBX2Fjtu2GATP0vSLLhT/7UV4LYojmOM94TePICgY=; b=f24qFiRN06FV8Q6HAi0lY87KLmG/HM/L+EVN5XKBufc5DYVBjPpFAAtlz30UYZpKuR D79JtmNOKPNLZ9/41CqLhFuwrMoRb0mttZ6cNy7ctUr2SxksFunrI4vRjtmj+DfWmgWY IHz6c3NsaBtttSvhUuG3eEDknb7neQxpAbD6gv6dHXNZUiMvKAgQP4eRaLe7kDGBFqkc Ak46rqF/m8gx8bakkJGyPM2YOfDKpLaYTy6+msve4S3tnvmubX7QDa0gVMDiIsydkLPb ZBPPgB92DsICs029s5PbijihkwTiNPGdNFatXgEhCPA0Ta9khqW4L5KPuxyiAyWCkQmO j3fw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=h77gyFLt; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: from out1.vger.email (out1.vger.email. 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[2.35.55.161]) by smtp.gmail.com with ESMTPSA id l10-20020a1ced0a000000b003c409244bb0sm134337wmh.6.2022.10.20.08.26.57 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Oct 2022 08:26:57 -0700 (PDT) From: Paolo Valente To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, glen.valante@linaro.org, arie.vanderhoeven@seagate.com, rory.c.chen@seagate.com, Paolo Valente , Gabriele Felici , Gianmarco Lusvardi , Giulio Barabino , Emiliano Maccaferri Subject: [PATCH V4 4/8] block, bfq: turn bfqq_data into an array in bfq_io_cq Date: Thu, 20 Oct 2022 17:26:39 +0200 Message-Id: <20221020152643.21199-5-paolo.valente@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20221020152643.21199-1-paolo.valente@linaro.org> References: <20221020152643.21199-1-paolo.valente@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747220904754200408?= X-GMAIL-MSGID: =?utf-8?q?1747220904754200408?= When a bfq_queue Q is merged with another queue, several pieces of information are saved about Q. These pieces are stored in the bfqq_data field in the bfq_io_cq data structure of the process associated with Q. Yet, with a multi-actuator drive, a process may get associated with multiple bfq_queues: one queue for each of the N actuators. Each of these queues may undergo a merge. So, the bfq_io_cq data structure must be able to accommodate the above information for N queues. This commit solves this problem by turning the bfqq_data scalar field into an array of N elements (and by changing code so as to handle this array). This solution is written under the assumption that bfq_queues associated with different actuators cannot be cross-merged. This assumption holds naturally with basic queue merging: the latter is triggered by spatial locality, and sectors for different actuators are not close to each other. As for stable cross-merging, the assumption here is that it is disabled. Signed-off-by: Gabriele Felici Signed-off-by: Gianmarco Lusvardi Signed-off-by: Giulio Barabino Signed-off-by: Emiliano Maccaferri Signed-off-by: Paolo Valente --- block/bfq-iosched.c | 152 +++++++++++++++++++++++++------------------- block/bfq-iosched.h | 12 ++-- 2 files changed, 95 insertions(+), 69 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index d2bd94ea2e95..80fb20fe0e41 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -406,7 +406,7 @@ void bic_set_bfqq(struct bfq_io_cq *bic, */ bic->bfqq[is_sync][actuator_idx] = bfqq; - if (bfqq && bic->bfqq_data->stable_merge_bfqq == bfqq) { + if (bfqq && bic->bfqq_data[actuator_idx]->stable_merge_bfqq == bfqq) { /* * Actually, these same instructions are executed also * in bfq_setup_cooperator, in case of abort or actual @@ -415,9 +415,9 @@ void bic_set_bfqq(struct bfq_io_cq *bic, * did so, we would nest even more complexity in this * function. */ - bfq_put_stable_ref(bic->bfqq_data->stable_merge_bfqq); + bfq_put_stable_ref(bic->bfqq_data[actuator_idx]->stable_merge_bfqq); - bic->bfqq_data->stable_merge_bfqq = NULL; + bic->bfqq_data[actuator_idx]->stable_merge_bfqq = NULL; } } @@ -1176,37 +1176,40 @@ bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd, { unsigned int old_wr_coeff = 1; bool busy = bfq_already_existing && bfq_bfqq_busy(bfqq); + unsigned int a_idx = bfqq->actuator_idx; - if (bic->bfqq_data->saved_has_short_ttime) + if (bic->bfqq_data[a_idx]->saved_has_short_ttime) bfq_mark_bfqq_has_short_ttime(bfqq); else bfq_clear_bfqq_has_short_ttime(bfqq); - if (bic->bfqq_data->saved_IO_bound) + if (bic->bfqq_data[a_idx]->saved_IO_bound) bfq_mark_bfqq_IO_bound(bfqq); else bfq_clear_bfqq_IO_bound(bfqq); - bfqq->last_serv_time_ns = bic->bfqq_data->saved_last_serv_time_ns; - bfqq->inject_limit = bic->bfqq_data->saved_inject_limit; - bfqq->decrease_time_jif = bic->bfqq_data->saved_decrease_time_jif; - - bfqq->entity.new_weight = bic->bfqq_data->saved_weight; - bfqq->ttime = bic->bfqq_data->saved_ttime; - bfqq->io_start_time = bic->bfqq_data->saved_io_start_time; - bfqq->tot_idle_time = bic->bfqq_data->saved_tot_idle_time; + bfqq->last_serv_time_ns = + bic->bfqq_data[a_idx]->saved_last_serv_time_ns; + bfqq->inject_limit = bic->bfqq_data[a_idx]->saved_inject_limit; + bfqq->decrease_time_jif = + bic->bfqq_data[a_idx]->saved_decrease_time_jif; + bfqq->entity.new_weight = bic->bfqq_data[a_idx]->saved_weight; + bfqq->ttime = bic->bfqq_data[a_idx]->saved_ttime; + bfqq->io_start_time = bic->bfqq_data[a_idx]->saved_io_start_time; + bfqq->tot_idle_time = bic->bfqq_data[a_idx]->saved_tot_idle_time; /* * Restore weight coefficient only if low_latency is on */ if (bfqd->low_latency) { old_wr_coeff = bfqq->wr_coeff; - bfqq->wr_coeff = bic->bfqq_data->saved_wr_coeff; + bfqq->wr_coeff = bic->bfqq_data[a_idx]->saved_wr_coeff; } - bfqq->service_from_wr = bic->bfqq_data->saved_service_from_wr; + bfqq->service_from_wr = bic->bfqq_data[a_idx]->saved_service_from_wr; bfqq->wr_start_at_switch_to_srt = - bic->bfqq_data->saved_wr_start_at_switch_to_srt; - bfqq->last_wr_start_finish = bic->bfqq_data->saved_last_wr_start_finish; - bfqq->wr_cur_max_time = bic->bfqq_data->saved_wr_cur_max_time; + bic->bfqq_data[a_idx]->saved_wr_start_at_switch_to_srt; + bfqq->last_wr_start_finish = + bic->bfqq_data[a_idx]->saved_last_wr_start_finish; + bfqq->wr_cur_max_time = bic->bfqq_data[a_idx]->saved_wr_cur_max_time; if (bfqq->wr_coeff > 1 && (bfq_bfqq_in_large_burst(bfqq) || time_is_before_jiffies(bfqq->last_wr_start_finish + @@ -1825,6 +1828,16 @@ static bool bfq_bfqq_higher_class_or_weight(struct bfq_queue *bfqq, return bfqq_weight > in_serv_weight; } +/* get the index of the actuator that will serve bio */ +static unsigned int bfq_actuator_index(struct bfq_data *bfqd, struct bio *bio) +{ + /* + * Multi-actuator support not complete yet, so always return 0 + * for the moment. + */ + return 0; +} + static bool bfq_better_to_idle(struct bfq_queue *bfqq); static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, @@ -1879,7 +1892,9 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, wr_or_deserves_wr = bfqd->low_latency && (bfqq->wr_coeff > 1 || (bfq_bfqq_sync(bfqq) && - (bfqq->bic || RQ_BIC(rq)->bfqq_data->stably_merged) && + (bfqq->bic || + RQ_BIC(rq)->bfqq_data[bfq_actuator_index(bfqd, rq->bio)] + ->stably_merged) && (*interactive || soft_rt))); /* @@ -2467,16 +2482,6 @@ static void bfq_remove_request(struct request_queue *q, } -/* get the index of the actuator that will serve bio */ -static unsigned int bfq_actuator_index(struct bfq_data *bfqd, struct bio *bio) -{ - /* - * Multi-actuator support not complete yet, so always return 0 - * for the moment. - */ - return 0; -} - static bool bfq_bio_merge(struct request_queue *q, struct bio *bio, unsigned int nr_segs) { @@ -2903,6 +2908,7 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, void *io_struct, bool request, struct bfq_io_cq *bic) { struct bfq_queue *in_service_bfqq, *new_bfqq; + unsigned int a_idx = bfqq->actuator_idx; /* if a merge has already been setup, then proceed with that first */ if (bfqq->new_bfqq) @@ -2924,21 +2930,22 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, * stable merging) also if bic is associated with a * sync queue, but this bfqq is async */ - if (bfq_bfqq_sync(bfqq) && bic->bfqq_data->stable_merge_bfqq && + if (bfq_bfqq_sync(bfqq) && + bic->bfqq_data[a_idx]->stable_merge_bfqq && !bfq_bfqq_just_created(bfqq) && time_is_before_jiffies(bfqq->split_time + msecs_to_jiffies(bfq_late_stable_merging)) && time_is_before_jiffies(bfqq->creation_time + msecs_to_jiffies(bfq_late_stable_merging))) { struct bfq_queue *stable_merge_bfqq = - bic->bfqq_data->stable_merge_bfqq; + bic->bfqq_data[a_idx]->stable_merge_bfqq; int proc_ref = min(bfqq_process_refs(bfqq), bfqq_process_refs(stable_merge_bfqq)); /* deschedule stable merge, because done or aborted here */ bfq_put_stable_ref(stable_merge_bfqq); - bic->bfqq_data->stable_merge_bfqq = NULL; + bic->bfqq_data[a_idx]->stable_merge_bfqq = NULL; if (!idling_boosts_thr_without_issues(bfqd, bfqq) && proc_ref > 0) { @@ -2947,10 +2954,12 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, bfq_setup_merge(bfqq, stable_merge_bfqq); if (new_bfqq) { - bic->bfqq_data->stably_merged = true; + bic->bfqq_data[a_idx]->stably_merged = + true; if (new_bfqq->bic) - new_bfqq->bic->bfqq_data->stably_merged = - true; + new_bfqq->bic->bfqq_data + [new_bfqq->actuator_idx] + ->stably_merged = true; } return new_bfqq; } else @@ -3049,6 +3058,8 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, static void bfq_bfqq_save_state(struct bfq_queue *bfqq) { struct bfq_io_cq *bic = bfqq->bic; + /* State must be saved for the right queue index. */ + unsigned int a_idx = bfqq->actuator_idx; /* * If !bfqq->bic, the queue is already shared or its requests @@ -3058,19 +3069,23 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq) if (!bic) return; - bic->bfqq_data->saved_last_serv_time_ns = bfqq->last_serv_time_ns; - bic->bfqq_data->saved_inject_limit = bfqq->inject_limit; - bic->bfqq_data->saved_decrease_time_jif = bfqq->decrease_time_jif; + bic->bfqq_data[a_idx]->saved_last_serv_time_ns = + bfqq->last_serv_time_ns; + bic->bfqq_data[a_idx]->saved_inject_limit = + bfqq->inject_limit; + bic->bfqq_data[a_idx]->saved_decrease_time_jif = + bfqq->decrease_time_jif; - bic->bfqq_data->saved_weight = bfqq->entity.orig_weight; - bic->bfqq_data->saved_ttime = bfqq->ttime; - bic->bfqq_data->saved_has_short_ttime = + bic->bfqq_data[a_idx]->saved_weight = bfqq->entity.orig_weight; + bic->bfqq_data[a_idx]->saved_ttime = bfqq->ttime; + bic->bfqq_data[a_idx]->saved_has_short_ttime = bfq_bfqq_has_short_ttime(bfqq); - bic->bfqq_data->saved_IO_bound = bfq_bfqq_IO_bound(bfqq); - bic->bfqq_data->saved_io_start_time = bfqq->io_start_time; - bic->bfqq_data->saved_tot_idle_time = bfqq->tot_idle_time; - bic->bfqq_data->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq); - bic->bfqq_data->was_in_burst_list = + bic->bfqq_data[a_idx]->saved_IO_bound = bfq_bfqq_IO_bound(bfqq); + bic->bfqq_data[a_idx]->saved_io_start_time = bfqq->io_start_time; + bic->bfqq_data[a_idx]->saved_tot_idle_time = bfqq->tot_idle_time; + bic->bfqq_data[a_idx]->saved_in_large_burst = + bfq_bfqq_in_large_burst(bfqq); + bic->bfqq_data[a_idx]->was_in_burst_list = !hlist_unhashed(&bfqq->burst_list_node); if (unlikely(bfq_bfqq_just_created(bfqq) && @@ -3085,21 +3100,23 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq) * to bfqq, so that to avoid that bfqq unjustly fails * to enjoy weight raising if split soon. */ - bic->bfqq_data->saved_wr_coeff = bfqq->bfqd->bfq_wr_coeff; - bic->bfqq_data->saved_wr_start_at_switch_to_srt = + bic->bfqq_data[a_idx]->saved_wr_coeff = + bfqq->bfqd->bfq_wr_coeff; + bic->bfqq_data[a_idx]->saved_wr_start_at_switch_to_srt = bfq_smallest_from_now(); - bic->bfqq_data->saved_wr_cur_max_time = + bic->bfqq_data[a_idx]->saved_wr_cur_max_time = bfq_wr_duration(bfqq->bfqd); - bic->bfqq_data->saved_last_wr_start_finish = jiffies; + bic->bfqq_data[a_idx]->saved_last_wr_start_finish = jiffies; } else { - bic->bfqq_data->saved_wr_coeff = bfqq->wr_coeff; - bic->bfqq_data->saved_wr_start_at_switch_to_srt = + bic->bfqq_data[a_idx]->saved_wr_coeff = bfqq->wr_coeff; + bic->bfqq_data[a_idx]->saved_wr_start_at_switch_to_srt = bfqq->wr_start_at_switch_to_srt; - bic->bfqq_data->saved_service_from_wr = + bic->bfqq_data[a_idx]->saved_service_from_wr = bfqq->service_from_wr; - bic->bfqq_data->saved_last_wr_start_finish = + bic->bfqq_data[a_idx]->saved_last_wr_start_finish = bfqq->last_wr_start_finish; - bic->bfqq_data->saved_wr_cur_max_time = bfqq->wr_cur_max_time; + bic->bfqq_data[a_idx]->saved_wr_cur_max_time = + bfqq->wr_cur_max_time; } } @@ -5429,8 +5446,8 @@ static void bfq_exit_icq(struct io_cq *icq) spin_lock_irqsave(&bfqd->lock, flags); for (act_idx = 0; act_idx < bfqd->num_actuators; act_idx++) { - if (bic->bfqq_data->stable_merge_bfqq) - bfq_put_stable_ref(bic->bfqq_data->stable_merge_bfqq); + if (bic->bfqq_data[act_idx]->stable_merge_bfqq) + bfq_put_stable_ref(bic->bfqq_data[act_idx]->stable_merge_bfqq); bfq_exit_icq_bfqq(bic, true, act_idx); bfq_exit_icq_bfqq(bic, false, act_idx); @@ -5618,6 +5635,7 @@ bfq_do_early_stable_merge(struct bfq_data *bfqd, struct bfq_queue *bfqq, struct bfq_io_cq *bic, struct bfq_queue *last_bfqq_created) { + unsigned int a_idx = last_bfqq_created->actuator_idx; struct bfq_queue *new_bfqq = bfq_setup_merge(bfqq, last_bfqq_created); @@ -5625,8 +5643,8 @@ bfq_do_early_stable_merge(struct bfq_data *bfqd, struct bfq_queue *bfqq, return bfqq; if (new_bfqq->bic) - new_bfqq->bic->bfqq_data->stably_merged = true; - bic->bfqq_data->stably_merged = true; + new_bfqq->bic->bfqq_data[a_idx]->stably_merged = true; + bic->bfqq_data[a_idx]->stably_merged = true; /* * Reusing merge functions. This implies that @@ -5756,7 +5774,8 @@ static struct bfq_queue *bfq_do_or_sched_stable_merge(struct bfq_data *bfqd, /* * Record the bfqq to merge to. */ - bic->bfqq_data->stable_merge_bfqq = last_bfqq_created; + bic->bfqq_data[last_bfqq_created->actuator_idx]->stable_merge_bfqq = + last_bfqq_created; } } @@ -6690,12 +6709,13 @@ static struct bfq_queue *bfq_get_bfqq_handle_split(struct bfq_data *bfqd, bic_set_bfqq(bic, bfqq, is_sync, act_idx); if (split && is_sync) { - if ((bic->bfqq_data->was_in_burst_list && bfqd->large_burst) || - bic->bfqq_data->saved_in_large_burst) + if ((bic->bfqq_data[act_idx]->was_in_burst_list && + bfqd->large_burst) || + bic->bfqq_data[act_idx]->saved_in_large_burst) bfq_mark_bfqq_in_large_burst(bfqq); else { bfq_clear_bfqq_in_large_burst(bfqq); - if (bic->bfqq_data->was_in_burst_list) + if (bic->bfqq_data[act_idx]->was_in_burst_list) /* * If bfqq was in the current * burst list before being @@ -6784,6 +6804,7 @@ static struct bfq_queue *bfq_init_rq(struct request *rq) struct bfq_queue *bfqq; bool new_queue = false; bool bfqq_already_existing = false, split = false; + unsigned int a_idx = bfq_actuator_index(bfqd, bio); if (unlikely(!rq->elv.icq)) return NULL; @@ -6810,12 +6831,13 @@ static struct bfq_queue *bfq_init_rq(struct request *rq) if (likely(!new_queue)) { /* If the queue was seeky for too long, break it apart. */ if (bfq_bfqq_coop(bfqq) && bfq_bfqq_split_coop(bfqq) && - !bic->bfqq_data->stably_merged) { + !bic->bfqq_data[a_idx]->stably_merged) { struct bfq_queue *old_bfqq = bfqq; /* Update bic before losing reference to bfqq */ if (bfq_bfqq_in_large_burst(bfqq)) - bic->bfqq_data->saved_in_large_burst = true; + bic->bfqq_data[a_idx]->saved_in_large_burst = + true; bfqq = bfq_split_bfqq(bic, bfqq); split = true; diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 6bc7bed97956..713c6559fe91 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -420,7 +420,7 @@ struct bfq_queue { struct bfq_iocq_bfqq_data { /* * Snapshot of the has_short_time flag before merging; taken - * to remember its value while the queue is merged, so as to + * to remember its values while the queue is merged, so as to * be able to restore it in case of split. */ bool saved_has_short_ttime; @@ -434,7 +434,7 @@ struct bfq_iocq_bfqq_data { u64 saved_tot_idle_time; /* - * Same purpose as the previous fields for the value of the + * Same purpose as the previous fields for the values of the * field keeping the queue's belonging to a large burst */ bool saved_in_large_burst; @@ -497,8 +497,12 @@ struct bfq_io_cq { uint64_t blkcg_serial_nr; /* the current blkcg serial */ #endif - /* persistent data for associated synchronous process queue */ - struct bfq_iocq_bfqq_data *bfqq_data; + /* + * Persistent data for associated synchronous process queues + * (one queue per actuator, see field bfqq above). 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[2.35.55.161]) by smtp.gmail.com with ESMTPSA id l10-20020a1ced0a000000b003c409244bb0sm134337wmh.6.2022.10.20.08.26.58 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Oct 2022 08:26:59 -0700 (PDT) From: Paolo Valente To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, glen.valante@linaro.org, arie.vanderhoeven@seagate.com, rory.c.chen@seagate.com, Davide Zini , Paolo Valente Subject: [PATCH V4 5/8] block, bfq: split also async bfq_queues on a per-actuator basis Date: Thu, 20 Oct 2022 17:26:40 +0200 Message-Id: <20221020152643.21199-6-paolo.valente@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20221020152643.21199-1-paolo.valente@linaro.org> References: <20221020152643.21199-1-paolo.valente@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747221074881932676?= X-GMAIL-MSGID: =?utf-8?q?1747221074881932676?= From: Davide Zini Similarly to sync bfq_queues, also async bfq_queues need to be split on a per-actuator basis. Signed-off-by: Paolo Valente Signed-off-by: Davide Zini --- block/bfq-iosched.c | 41 +++++++++++++++++++++++------------------ block/bfq-iosched.h | 8 ++++---- 2 files changed, 27 insertions(+), 22 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 80fb20fe0e41..7c9b5cae05b5 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2673,14 +2673,16 @@ static void bfq_bfqq_end_wr(struct bfq_queue *bfqq) void bfq_end_wr_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg) { - int i, j; - - for (i = 0; i < 2; i++) - for (j = 0; j < IOPRIO_NR_LEVELS; j++) - if (bfqg->async_bfqq[i][j]) - bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]); - if (bfqg->async_idle_bfqq) - bfq_bfqq_end_wr(bfqg->async_idle_bfqq); + int i, j, k; + + for (k = 0; k < bfqd->num_actuators; k++) { + for (i = 0; i < 2; i++) + for (j = 0; j < IOPRIO_NR_LEVELS; j++) + if (bfqg->async_bfqq[i][j][k]) + bfq_bfqq_end_wr(bfqg->async_bfqq[i][j][k]); + if (bfqg->async_idle_bfqq[k]) + bfq_bfqq_end_wr(bfqg->async_idle_bfqq[k]); + } } static void bfq_end_wr(struct bfq_data *bfqd) @@ -5613,18 +5615,18 @@ static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, static struct bfq_queue **bfq_async_queue_prio(struct bfq_data *bfqd, struct bfq_group *bfqg, - int ioprio_class, int ioprio) + int ioprio_class, int ioprio, int act_idx) { switch (ioprio_class) { case IOPRIO_CLASS_RT: - return &bfqg->async_bfqq[0][ioprio]; + return &bfqg->async_bfqq[0][ioprio][act_idx]; case IOPRIO_CLASS_NONE: ioprio = IOPRIO_BE_NORM; fallthrough; case IOPRIO_CLASS_BE: - return &bfqg->async_bfqq[1][ioprio]; + return &bfqg->async_bfqq[1][ioprio][act_idx]; case IOPRIO_CLASS_IDLE: - return &bfqg->async_idle_bfqq; + return &bfqg->async_idle_bfqq[act_idx]; default: return NULL; } @@ -5798,7 +5800,8 @@ static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, if (!is_sync) { async_bfqq = bfq_async_queue_prio(bfqd, bfqg, ioprio_class, - ioprio); + ioprio, + bfq_actuator_index(bfqd, bio)); bfqq = *async_bfqq; if (bfqq) goto out; @@ -7015,13 +7018,15 @@ static void __bfq_put_async_bfqq(struct bfq_data *bfqd, */ void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg) { - int i, j; + int i, j, k; - for (i = 0; i < 2; i++) - for (j = 0; j < IOPRIO_NR_LEVELS; j++) - __bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]); + for (k = 0; k < bfqd->num_actuators; k++) { + for (i = 0; i < 2; i++) + for (j = 0; j < IOPRIO_NR_LEVELS; j++) + __bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j][k]); - __bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq); + __bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq[k]); + } } /* diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 713c6559fe91..5fca86a82411 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -980,8 +980,8 @@ struct bfq_group { void *bfqd; - struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS]; - struct bfq_queue *async_idle_bfqq; + struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS][BFQ_MAX_ACTUATORS]; + struct bfq_queue *async_idle_bfqq[BFQ_MAX_ACTUATORS]; struct bfq_entity *my_entity; @@ -997,8 +997,8 @@ struct bfq_group { struct bfq_entity entity; struct bfq_sched_data sched_data; - struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS]; - struct bfq_queue *async_idle_bfqq; + struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS][BFQ_MAX_ACTUATORS]; + struct bfq_queue *async_idle_bfqq[BFQ_MAX_ACTUATORS]; struct rb_root rq_pos_tree; }; From patchwork Thu Oct 20 15:26:41 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Valente X-Patchwork-Id: 6258 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4242:0:0:0:0:0 with SMTP id s2csp174140wrr; Thu, 20 Oct 2022 08:29:56 -0700 (PDT) X-Google-Smtp-Source: AMsMyM44kJwKpLNnk8tn22zjMBtOs15fhKkCZ4UaPH9Sj9lHkn3JNo7zz3Sl8XwupszbFMgVlNIg X-Received: by 2002:a17:907:2c4a:b0:78d:ee99:a06b with SMTP id hf10-20020a1709072c4a00b0078dee99a06bmr10986263ejc.578.1666279795952; Thu, 20 Oct 2022 08:29:55 -0700 (PDT) ARC-Seal: i=1; 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[2.35.55.161]) by smtp.gmail.com with ESMTPSA id l10-20020a1ced0a000000b003c409244bb0sm134337wmh.6.2022.10.20.08.26.59 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Oct 2022 08:27:00 -0700 (PDT) From: Paolo Valente To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, glen.valante@linaro.org, arie.vanderhoeven@seagate.com, rory.c.chen@seagate.com, Federico Gavioli , Paolo Valente Subject: [PATCH V4 6/8] block, bfq: retrieve independent access ranges from request queue Date: Thu, 20 Oct 2022 17:26:41 +0200 Message-Id: <20221020152643.21199-7-paolo.valente@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20221020152643.21199-1-paolo.valente@linaro.org> References: <20221020152643.21199-1-paolo.valente@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747221003198657348?= X-GMAIL-MSGID: =?utf-8?q?1747221003198657348?= From: Federico Gavioli This patch implements the code to gather the content of the independent_access_ranges structure from the request_queue and copy it into the queue's bfq_data. This copy is done at queue initialization. We copy the access ranges into the bfq_data to avoid taking the queue lock each time we access the ranges. This implementation, however, puts a limit to the maximum independent ranges supported by the scheduler. Such a limit is equal to the constant BFQ_MAX_ACTUATORS. This limit was placed to avoid the allocation of dynamic memory. Co-developed-by: Rory Chen Signed-off-by: Rory Chen Signed-off-by: Federico Gavioli Signed-off-by: Paolo Valente --- block/bfq-iosched.c | 54 ++++++++++++++++++++++++++++++++++++++------- block/bfq-iosched.h | 5 +++++ 2 files changed, 51 insertions(+), 8 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 7c9b5cae05b5..d0109bfc2ed0 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -1831,10 +1831,26 @@ static bool bfq_bfqq_higher_class_or_weight(struct bfq_queue *bfqq, /* get the index of the actuator that will serve bio */ static unsigned int bfq_actuator_index(struct bfq_data *bfqd, struct bio *bio) { - /* - * Multi-actuator support not complete yet, so always return 0 - * for the moment. - */ + struct blk_independent_access_range *iar; + unsigned int i; + sector_t end; + + /* no search needed if one or zero ranges present */ + if (bfqd->num_actuators < 2) + return 0; + + /* bio_end_sector(bio) gives the sector after the last one */ + end = bio_end_sector(bio) - 1; + + for (i = 0; i < bfqd->num_actuators; i++) { + iar = &(bfqd->ia_ranges[i]); + if (end >= iar->sector && end < iar->sector + iar->nr_sectors) + return i; + } + + WARN_ONCE(true, + "bfq_actuator_index: bio sector out of ranges: end=%llu\n", + end); return 0; } @@ -2479,7 +2495,6 @@ static void bfq_remove_request(struct request_queue *q, if (rq->cmd_flags & REQ_META) bfqq->meta_pending--; - } static bool bfq_bio_merge(struct request_queue *q, struct bio *bio, @@ -7137,6 +7152,8 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e) { struct bfq_data *bfqd; struct elevator_queue *eq; + unsigned int i; + struct blk_independent_access_ranges *ia_ranges = q->disk->ia_ranges; eq = elevator_alloc(q, e); if (!eq) @@ -7180,10 +7197,31 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e) bfqd->queue = q; /* - * Multi-actuator support not complete yet, default to single - * actuator for the moment. + * If the disk supports multiple actuators, we copy the independent + * access ranges from the request queue structure. */ - bfqd->num_actuators = 1; + spin_lock_irq(&q->queue_lock); + if (ia_ranges) { + /* + * Check if the disk ia_ranges size exceeds the current bfq + * actuator limit. + */ + if (ia_ranges->nr_ia_ranges > BFQ_MAX_ACTUATORS) { + pr_crit("nr_ia_ranges higher than act limit: iars=%d, max=%d.\n", + ia_ranges->nr_ia_ranges, BFQ_MAX_ACTUATORS); + pr_crit("Falling back to single actuator mode.\n"); + bfqd->num_actuators = 0; + } else { + bfqd->num_actuators = ia_ranges->nr_ia_ranges; + + for (i = 0; i < bfqd->num_actuators; i++) + bfqd->ia_ranges[i] = ia_ranges->ia_range[i]; + } + } else { + bfqd->num_actuators = 0; + } + + spin_unlock_irq(&q->queue_lock); INIT_LIST_HEAD(&bfqd->dispatch); diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 5fca86a82411..326d68d65cc9 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -815,6 +815,11 @@ struct bfq_data { */ unsigned int num_actuators; + /* + * Disk independent access ranges for each actuator + * in this device. + */ + struct blk_independent_access_range ia_ranges[BFQ_MAX_ACTUATORS]; 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[2.35.55.161]) by smtp.gmail.com with ESMTPSA id l10-20020a1ced0a000000b003c409244bb0sm134337wmh.6.2022.10.20.08.27.01 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Oct 2022 08:27:02 -0700 (PDT) From: Paolo Valente To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, glen.valante@linaro.org, arie.vanderhoeven@seagate.com, rory.c.chen@seagate.com, Davide Zini , Paolo Valente Subject: [PATCH V4 7/8] block, bfq: inject I/O to underutilized actuators Date: Thu, 20 Oct 2022 17:26:42 +0200 Message-Id: <20221020152643.21199-8-paolo.valente@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20221020152643.21199-1-paolo.valente@linaro.org> References: <20221020152643.21199-1-paolo.valente@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747221039064783490?= X-GMAIL-MSGID: =?utf-8?q?1747221039064783490?= From: Davide Zini The main service scheme of BFQ for sync I/O is serving one sync bfq_queue at a time, for a while. In particular, BFQ enforces this scheme when it deems the latter necessary to boost throughput or to preserve service guarantees. Unfortunately, when BFQ enforces this policy, only one actuator at a time gets served for a while, because each bfq_queue contains I/O only for one actuator. The other actuators may remain underutilized. Actually, BFQ may serve (inject) extra I/O, taken from other bfq_queues, in parallel with that of the in-service queue. This injection mechanism may provide the ground for dealing also with the above actuator-underutilization problem. Yet BFQ does not take the actuator load into account when choosing which queue to pick extra I/O from. In addition, BFQ may happen to inject extra I/O only when the in-service queue is temporarily empty. In view of these facts, this commit extends the injection mechanism in such a way that the latter: (1) takes into account also the actuator load; (2) checks such a load on each dispatch, and injects I/O for an underutilized actuator, if there is one and there is I/O for it. To perform the check in (2), this commit introduces a load threshold, currently set to 4. A linear scan of each actuator is performed, until an actuator is found for which the following two conditions hold: the load of the actuator is below the threshold, and there is at least one non-in-service queue that contains I/O for that actuator. If such a pair (actuator, queue) is found, then the head request of that queue is returned for dispatch, instead of the head request of the in-service queue. We have set the threshold, empirically, to the minimum possible value for which an actuator is fully utilized, or close to be fully utilized. By doing so, injected I/O 'steals' as few drive-queue slots as possibile to the in-service queue. This reduces as much as possible the probability that the service of I/O from the in-service bfq_queue gets delayed because of slot exhaustion, i.e., because all the slots of the drive queue are filled with I/O injected from other queues (NCQ provides for 32 slots). This new mechanism also counters actuator underutilization in the case of asymmetric configurations of bfq_queues. Namely if there are few bfq_queues containing I/O for some actuators and many bfq_queues containing I/O for other actuators. Or if the bfq_queues containing I/O for some actuators have lower weights than the other bfq_queues. Signed-off-by: Paolo Valente Signed-off-by: Davide Zini --- block/bfq-cgroup.c | 2 +- block/bfq-iosched.c | 139 +++++++++++++++++++++++++++++++++----------- block/bfq-iosched.h | 39 ++++++++++++- block/bfq-wf2q.c | 2 +- 4 files changed, 143 insertions(+), 39 deletions(-) diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index d243c429d9c0..38ccfe55ad46 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -694,7 +694,7 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, bfq_activate_bfqq(bfqd, bfqq); } - if (!bfqd->in_service_queue && !bfqd->rq_in_driver) + if (!bfqd->in_service_queue && !bfqd->tot_rq_in_driver) bfq_schedule_dispatch(bfqd); /* release extra ref taken above, bfqq may happen to be freed now */ bfq_put_queue(bfqq); diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index d0109bfc2ed0..77d3ddabf059 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2252,6 +2252,7 @@ static void bfq_add_request(struct request *rq) bfq_log_bfqq(bfqd, bfqq, "add_request %d", rq_is_sync(rq)); bfqq->queued[rq_is_sync(rq)]++; + /* * Updating of 'bfqd->queued' is protected by 'bfqd->lock', however, it * may be read without holding the lock in bfq_has_work(). @@ -2297,9 +2298,9 @@ static void bfq_add_request(struct request *rq) * elapsed. */ if (bfqq == bfqd->in_service_queue && - (bfqd->rq_in_driver == 0 || + (bfqd->tot_rq_in_driver == 0 || (bfqq->last_serv_time_ns > 0 && - bfqd->rqs_injected && bfqd->rq_in_driver > 0)) && + bfqd->rqs_injected && bfqd->tot_rq_in_driver > 0)) && time_is_before_eq_jiffies(bfqq->decrease_time_jif + msecs_to_jiffies(10))) { bfqd->last_empty_occupied_ns = ktime_get_ns(); @@ -2323,7 +2324,7 @@ static void bfq_add_request(struct request *rq) * will be set in case injection is performed * on bfqq before rq is completed). */ - if (bfqd->rq_in_driver == 0) + if (bfqd->tot_rq_in_driver == 0) bfqd->rqs_injected = false; } } @@ -2421,15 +2422,18 @@ static sector_t get_sdist(sector_t last_pos, struct request *rq) static void bfq_activate_request(struct request_queue *q, struct request *rq) { struct bfq_data *bfqd = q->elevator->elevator_data; + unsigned int act_idx = bfq_actuator_index(bfqd, rq->bio); - bfqd->rq_in_driver++; + bfqd->tot_rq_in_driver++; + bfqd->rq_in_driver[act_idx]++; } static void bfq_deactivate_request(struct request_queue *q, struct request *rq) { struct bfq_data *bfqd = q->elevator->elevator_data; - bfqd->rq_in_driver--; + bfqd->tot_rq_in_driver--; + bfqd->rq_in_driver[bfq_actuator_index(bfqd, rq->bio)]--; } #endif @@ -2703,11 +2707,14 @@ void bfq_end_wr_async_queues(struct bfq_data *bfqd, static void bfq_end_wr(struct bfq_data *bfqd) { struct bfq_queue *bfqq; + int i; spin_lock_irq(&bfqd->lock); - list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list) - bfq_bfqq_end_wr(bfqq); + for (i = 0; i < bfqd->num_actuators; i++) { + list_for_each_entry(bfqq, &bfqd->active_list[i], bfqq_list) + bfq_bfqq_end_wr(bfqq); + } list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list) bfq_bfqq_end_wr(bfqq); bfq_end_wr_async(bfqd); @@ -3657,13 +3664,13 @@ static void bfq_update_peak_rate(struct bfq_data *bfqd, struct request *rq) * - start a new observation interval with this dispatch */ if (now_ns - bfqd->last_dispatch > 100*NSEC_PER_MSEC && - bfqd->rq_in_driver == 0) + bfqd->tot_rq_in_driver == 0) goto update_rate_and_reset; /* Update sampling information */ bfqd->peak_rate_samples++; - if ((bfqd->rq_in_driver > 0 || + if ((bfqd->tot_rq_in_driver > 0 || now_ns - bfqd->last_completion < BFQ_MIN_TT) && !BFQ_RQ_SEEKY(bfqd, bfqd->last_position, rq)) bfqd->sequential_samples++; @@ -3930,7 +3937,7 @@ static bool idling_needed_for_service_guarantees(struct bfq_data *bfqd, return (bfqq->wr_coeff > 1 && (bfqd->wr_busy_queues < tot_busy_queues || - bfqd->rq_in_driver >= + bfqd->tot_rq_in_driver >= bfqq->dispatched + 4)) || bfq_asymmetric_scenario(bfqd, bfqq) || tot_busy_queues == 1; @@ -4702,6 +4709,7 @@ bfq_choose_bfqq_for_injection(struct bfq_data *bfqd) { struct bfq_queue *bfqq, *in_serv_bfqq = bfqd->in_service_queue; unsigned int limit = in_serv_bfqq->inject_limit; + int i; /* * If * - bfqq is not weight-raised and therefore does not carry @@ -4733,7 +4741,7 @@ bfq_choose_bfqq_for_injection(struct bfq_data *bfqd) ) limit = 1; - if (bfqd->rq_in_driver >= limit) + if (bfqd->tot_rq_in_driver >= limit) return NULL; /* @@ -4748,11 +4756,12 @@ bfq_choose_bfqq_for_injection(struct bfq_data *bfqd) * (and re-added only if it gets new requests, but then it * is assigned again enough budget for its new backlog). */ - list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list) - if (!RB_EMPTY_ROOT(&bfqq->sort_list) && - (in_serv_always_inject || bfqq->wr_coeff > 1) && - bfq_serv_to_charge(bfqq->next_rq, bfqq) <= - bfq_bfqq_budget_left(bfqq)) { + for (i = 0; i < bfqd->num_actuators; i++) { + list_for_each_entry(bfqq, &bfqd->active_list[i], bfqq_list) + if (!RB_EMPTY_ROOT(&bfqq->sort_list) && + (in_serv_always_inject || bfqq->wr_coeff > 1) && + bfq_serv_to_charge(bfqq->next_rq, bfqq) <= + bfq_bfqq_budget_left(bfqq)) { /* * Allow for only one large in-flight request * on non-rotational devices, for the @@ -4777,22 +4786,69 @@ bfq_choose_bfqq_for_injection(struct bfq_data *bfqd) else limit = in_serv_bfqq->inject_limit; - if (bfqd->rq_in_driver < limit) { + if (bfqd->tot_rq_in_driver < limit) { bfqd->rqs_injected = true; return bfqq; } } + } + + return NULL; +} + +static struct bfq_queue * +bfq_find_active_bfqq_for_actuator(struct bfq_data *bfqd, + int idx) +{ + struct bfq_queue *bfqq = NULL; + + if (bfqd->in_service_queue && + bfqd->in_service_queue->actuator_idx == idx) + return bfqd->in_service_queue; + + list_for_each_entry(bfqq, &bfqd->active_list[idx], bfqq_list) { + if (!RB_EMPTY_ROOT(&bfqq->sort_list) && + bfq_serv_to_charge(bfqq->next_rq, bfqq) <= + bfq_bfqq_budget_left(bfqq)) { + return bfqq; + } + } return NULL; } +/* + * Perform a linear scan of each actuator, until an actuator is found + * for which the following two conditions hold: the load of the + * actuator is below the threshold (see comments on actuator_load_threshold + * for details), and there is a queue that contains I/O for that + * actuator. On success, return that queue. + */ +static struct bfq_queue * +bfq_find_bfqq_for_underused_actuator(struct bfq_data *bfqd) +{ + int i; + + for (i = 0 ; i < bfqd->num_actuators; i++) + if (bfqd->rq_in_driver[i] < bfqd->actuator_load_threshold) { + struct bfq_queue *bfqq = + bfq_find_active_bfqq_for_actuator(bfqd, i); + + if (bfqq) + return bfqq; + } + + return NULL; +} + + /* * Select a queue for service. If we have a current queue in service, * check whether to continue servicing it, or retrieve and set a new one. */ static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd) { - struct bfq_queue *bfqq; + struct bfq_queue *bfqq, *inject_bfqq; struct request *next_rq; enum bfqq_expiration reason = BFQQE_BUDGET_TIMEOUT; @@ -4814,6 +4870,15 @@ static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd) goto expire; check_queue: + /* + * If some actuator is underutilized, but the in-service + * queue does not contain I/O for that actuator, then try to + * inject I/O for that actuator. + */ + inject_bfqq = bfq_find_bfqq_for_underused_actuator(bfqd); + if (inject_bfqq && inject_bfqq != bfqq) + return inject_bfqq; + /* * This loop is rarely executed more than once. Even when it * happens, it is much more convenient to re-execute this loop @@ -5169,11 +5234,11 @@ static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) /* * We exploit the bfq_finish_requeue_request hook to - * decrement rq_in_driver, but + * decrement tot_rq_in_driver, but * bfq_finish_requeue_request will not be invoked on * this request. So, to avoid unbalance, just start - * this request, without incrementing rq_in_driver. As - * a negative consequence, rq_in_driver is deceptively + * this request, without incrementing tot_rq_in_driver. As + * a negative consequence, tot_rq_in_driver is deceptively * lower than it should be while this request is in * service. This may cause bfq_schedule_dispatch to be * invoked uselessly. @@ -5182,7 +5247,7 @@ static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) * bfq_finish_requeue_request hook, if defined, is * probably invoked also on this request. So, by * exploiting this hook, we could 1) increment - * rq_in_driver here, and 2) decrement it in + * tot_rq_in_driver here, and 2) decrement it in * bfq_finish_requeue_request. Such a solution would * let the value of the counter be always accurate, * but it would entail using an extra interface @@ -5211,7 +5276,7 @@ static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) * Of course, serving one request at a time may cause loss of * throughput. */ - if (bfqd->strict_guarantees && bfqd->rq_in_driver > 0) + if (bfqd->strict_guarantees && bfqd->tot_rq_in_driver > 0) goto exit; bfqq = bfq_select_queue(bfqd); @@ -5222,7 +5287,8 @@ static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx) if (rq) { inc_in_driver_start_rq: - bfqd->rq_in_driver++; + bfqd->rq_in_driver[bfqq->actuator_idx]++; + bfqd->tot_rq_in_driver++; start_rq: rq->rq_flags |= RQF_STARTED; } @@ -6282,7 +6348,7 @@ static void bfq_update_hw_tag(struct bfq_data *bfqd) struct bfq_queue *bfqq = bfqd->in_service_queue; bfqd->max_rq_in_driver = max_t(int, bfqd->max_rq_in_driver, - bfqd->rq_in_driver); + bfqd->tot_rq_in_driver); if (bfqd->hw_tag == 1) return; @@ -6293,7 +6359,7 @@ static void bfq_update_hw_tag(struct bfq_data *bfqd) * sum is not exact, as it's not taking into account deactivated * requests. */ - if (bfqd->rq_in_driver + bfqd->queued <= BFQ_HW_QUEUE_THRESHOLD) + if (bfqd->tot_rq_in_driver + bfqd->queued <= BFQ_HW_QUEUE_THRESHOLD) return; /* @@ -6304,7 +6370,7 @@ static void bfq_update_hw_tag(struct bfq_data *bfqd) if (bfqq && bfq_bfqq_has_short_ttime(bfqq) && bfqq->dispatched + bfqq->queued[0] + bfqq->queued[1] < BFQ_HW_QUEUE_THRESHOLD && - bfqd->rq_in_driver < BFQ_HW_QUEUE_THRESHOLD) + bfqd->tot_rq_in_driver < BFQ_HW_QUEUE_THRESHOLD) return; if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES) @@ -6325,7 +6391,8 @@ static void bfq_completed_request(struct bfq_queue *bfqq, struct bfq_data *bfqd) bfq_update_hw_tag(bfqd); - bfqd->rq_in_driver--; + bfqd->rq_in_driver[bfqq->actuator_idx]--; + bfqd->tot_rq_in_driver--; bfqq->dispatched--; if (!bfqq->dispatched && !bfq_bfqq_busy(bfqq)) { @@ -6444,7 +6511,7 @@ static void bfq_completed_request(struct bfq_queue *bfqq, struct bfq_data *bfqd) BFQQE_NO_MORE_REQUESTS); } - if (!bfqd->rq_in_driver) + if (!bfqd->tot_rq_in_driver) bfq_schedule_dispatch(bfqd); } @@ -6575,13 +6642,13 @@ static void bfq_update_inject_limit(struct bfq_data *bfqd, * conditions to do it, or we can lower the last base value * computed. * - * NOTE: (bfqd->rq_in_driver == 1) means that there is no I/O + * NOTE: (bfqd->tot_rq_in_driver == 1) means that there is no I/O * request in flight, because this function is in the code * path that handles the completion of a request of bfqq, and, * in particular, this function is executed before - * bfqd->rq_in_driver is decremented in such a code path. + * bfqd->tot_rq_in_driver is decremented in such a code path. */ - if ((bfqq->last_serv_time_ns == 0 && bfqd->rq_in_driver == 1) || + if ((bfqq->last_serv_time_ns == 0 && bfqd->tot_rq_in_driver == 1) || tot_time_ns < bfqq->last_serv_time_ns) { if (bfqq->last_serv_time_ns == 0) { /* @@ -6591,7 +6658,7 @@ static void bfq_update_inject_limit(struct bfq_data *bfqd, bfqq->inject_limit = max_t(unsigned int, 1, old_limit); } bfqq->last_serv_time_ns = tot_time_ns; - } else if (!bfqd->rqs_injected && bfqd->rq_in_driver == 1) + } else if (!bfqd->rqs_injected && bfqd->tot_rq_in_driver == 1) /* * No I/O injected and no request still in service in * the drive: these are the exact conditions for @@ -7232,7 +7299,8 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e) bfqd->queue_weights_tree = RB_ROOT_CACHED; bfqd->num_groups_with_pending_reqs = 0; - INIT_LIST_HEAD(&bfqd->active_list); + INIT_LIST_HEAD(&bfqd->active_list[0]); + INIT_LIST_HEAD(&bfqd->active_list[1]); INIT_LIST_HEAD(&bfqd->idle_list); INIT_HLIST_HEAD(&bfqd->burst_list); @@ -7277,6 +7345,9 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e) ref_wr_duration[blk_queue_nonrot(bfqd->queue)]; bfqd->peak_rate = ref_rate[blk_queue_nonrot(bfqd->queue)] * 2 / 3; + /* see comments on the definition of next field inside bfq_data */ + bfqd->actuator_load_threshold = 4; + spin_lock_init(&bfqd->lock); /* diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h index 326d68d65cc9..247717b7ffa5 100644 --- a/block/bfq-iosched.h +++ b/block/bfq-iosched.h @@ -590,7 +590,12 @@ struct bfq_data { /* number of queued requests */ int queued; /* number of requests dispatched and waiting for completion */ - int rq_in_driver; + int tot_rq_in_driver; + /* + * number of requests dispatched and waiting for completion + * for each actuator + */ + int rq_in_driver[BFQ_MAX_ACTUATORS]; /* true if the device is non rotational and performs queueing */ bool nonrot_with_queueing; @@ -684,8 +689,13 @@ struct bfq_data { /* maximum budget allotted to a bfq_queue before rescheduling */ int bfq_max_budget; - /* list of all the bfq_queues active on the device */ - struct list_head active_list; + /* + * List of all the bfq_queues active for a specific actuator + * on the device. Keeping active queues separate on a + * per-actuator basis helps implementing per-actuator + * injection more efficiently. + */ + struct list_head active_list[BFQ_MAX_ACTUATORS]; /* list of all the bfq_queues idle on the device */ struct list_head idle_list; @@ -820,6 +830,29 @@ struct bfq_data { * in this device. */ struct blk_independent_access_range ia_ranges[BFQ_MAX_ACTUATORS]; + + /* + * If the number of I/O requests queued in the device for a + * given actuator is below next threshold, then the actuator + * is deemed as underutilized. If this condition is found to + * hold for some actuator upon a dispatch, but (i) the + * in-service queue does not contain I/O for that actuator, + * while (ii) some other queue does contain I/O for that + * actuator, then the head I/O request of the latter queue is + * returned (injected), instead of the head request of the + * currently in-service queue. + * + * We set the threshold, empirically, to the minimum possible + * value for which an actuator is fully utilized, or close to + * be fully utilized. By doing so, injected I/O 'steals' as + * few drive-queue slots as possibile to the in-service + * queue. This reduces as much as possible the probability + * that the service of I/O from the in-service bfq_queue gets + * delayed because of slot exhaustion, i.e., because all the + * slots of the drive queue are filled with I/O injected from + * other queues (NCQ provides for 32 slots). + */ + unsigned int actuator_load_threshold; }; enum bfqq_state_flags { diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c index 8fc3da4c23bb..ec0273e2cd07 100644 --- a/block/bfq-wf2q.c +++ b/block/bfq-wf2q.c @@ -477,7 +477,7 @@ static void bfq_active_insert(struct bfq_service_tree *st, bfqd = (struct bfq_data *)bfqg->bfqd; #endif if (bfqq) - list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list); + list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list[bfqq->actuator_idx]); #ifdef CONFIG_BFQ_GROUP_IOSCHED if (bfqg != bfqd->root_group) bfqg->active_entities++; From patchwork Thu Oct 20 15:26:43 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Valente X-Patchwork-Id: 6261 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4242:0:0:0:0:0 with SMTP id s2csp180993wrr; Thu, 20 Oct 2022 08:42:41 -0700 (PDT) X-Google-Smtp-Source: AMsMyM6pmMHEhpMRlROqraEVBqVFAZ+zB//t4tH8yhY6Co4icxvDT85xLS1v8QznCyr65v9SvIkc X-Received: by 2002:a05:6402:5193:b0:45c:e2c6:6f0e with SMTP id q19-20020a056402519300b0045ce2c66f0emr13028206edd.29.1666280560961; Thu, 20 Oct 2022 08:42:40 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1666280560; cv=none; d=google.com; s=arc-20160816; b=FJEdD4I/ztrTMYNgbpekvR+e6Am+RVljdlwaBj7loSLnjKIZwPtwcRt93mndyj+IbQ 8X2/O16ODf7QN/UT1ev9WAR0lenFs+ccHLAQlFMwVM8DJj6xfdXmUNuQVTgqGrOBFmof P0cDxbarh76MIzmPZah7pt0nHp+K+vOpYvCZb8TD7Dw5UK5AP2Cg/gmgpb2MFj5rojix /mXREKYNGaMGFERdtC111cudfCU9Fp2qWZLqKOESsI/2c4H6ml0wcRiQPjFjnXQ5lPZH CA2ar77qpws+QjDl3ea6yzIlT+ROw3S3LsPpo+Iso3ELr6IAoIb/qW2lhbjyMCwB52Rk T+Bg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=XCbyLMSIwCFaLYXKLCOo4G7nJD5L3ekihEuWwF8mvwE=; b=HSTivde2p0azzh8H7r/bSQnM6LMRVuUHKrHoL/nRxSc08jtZEwfbesCSIcTEBR+dnY KsV8PpasB17jkg9Z9qrUVMEuZXnY0RpGJDN1R7mIeOmIMKld5x14Dx7pwOw1AbeLZeHt xQ2ByB1WlgkMFSvAz2X2nXqdGgksWKb8ff4uqoWZZGk94jYSuBefhJWuXzwnoymEzCxr 6XqtX92ZY3qBblA0MW8ETHw+7lgT7E/mkzGRa3v48GsIjb+AbLGRMKyUZZd/FPN++r7b M6hh5Lin9/YTO4sm9LPNdGdMwQ/sw4v/GWUZCukB1himq2i/OUIvRtJ2ozMxmNvgKUTQ deNQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=AHsOeapv; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: from out1.vger.email (out1.vger.email. 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[2.35.55.161]) by smtp.gmail.com with ESMTPSA id l10-20020a1ced0a000000b003c409244bb0sm134337wmh.6.2022.10.20.08.27.02 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Oct 2022 08:27:03 -0700 (PDT) From: Paolo Valente To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, glen.valante@linaro.org, arie.vanderhoeven@seagate.com, rory.c.chen@seagate.com, Davide Zini , Paolo Valente Subject: [PATCH V4 8/8] block, bfq: balance I/O injection among underutilized actuators Date: Thu, 20 Oct 2022 17:26:43 +0200 Message-Id: <20221020152643.21199-9-paolo.valente@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20221020152643.21199-1-paolo.valente@linaro.org> References: <20221020152643.21199-1-paolo.valente@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747221805546430710?= X-GMAIL-MSGID: =?utf-8?q?1747221805546430710?= From: Davide Zini Upon the invocation of its dispatch function, BFQ returns the next I/O request of the in-service bfq_queue, unless some exception holds. One such exception is that there is some underutilized actuator, different from the actuator for which the in-service queue contains I/O, and that some other bfq_queue happens to contain I/O for such an actuator. In this case, the next I/O request of the latter bfq_queue, and not of the in-service bfq_queue, is returned (I/O is injected from that bfq_queue). To find such an actuator, a linear scan, in increasing index order, is performed among actuators. Performing a linear scan entails a prioritization among actuators: an underutilized actuator may be considered for injection only if all actuators with a lower index are currently fully utilized, or if there is no pending I/O for any lower-index actuator that happens to be underutilized. This commits breaks this prioritization and tends to distribute injection uniformly across actuators. This is obtained by adding the following condition to the linear scan: even if an actuator A is underutilized, A is however skipped if its load is higher than that of the next actuator. Signed-off-by: Paolo Valente Signed-off-by: Davide Zini --- block/bfq-iosched.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 77d3ddabf059..b178dfe8a5c8 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -4819,10 +4819,16 @@ bfq_find_active_bfqq_for_actuator(struct bfq_data *bfqd, /* * Perform a linear scan of each actuator, until an actuator is found - * for which the following two conditions hold: the load of the - * actuator is below the threshold (see comments on actuator_load_threshold - * for details), and there is a queue that contains I/O for that - * actuator. On success, return that queue. + * for which the following three conditions hold: the load of the + * actuator is below the threshold (see comments on + * actuator_load_threshold for details) and lower than that of the + * next actuator (comments on this extra condition below), and there + * is a queue that contains I/O for that actuator. On success, return + * that queue. + * + * Performing a plain linear scan entails a prioritization among + * actuators. The extra condition above breaks this prioritization and + * tends to distribute injection uniformly across actuators. */ static struct bfq_queue * bfq_find_bfqq_for_underused_actuator(struct bfq_data *bfqd) @@ -4830,7 +4836,9 @@ bfq_find_bfqq_for_underused_actuator(struct bfq_data *bfqd) int i; for (i = 0 ; i < bfqd->num_actuators; i++) - if (bfqd->rq_in_driver[i] < bfqd->actuator_load_threshold) { + if (bfqd->rq_in_driver[i] < bfqd->actuator_load_threshold && + (i == bfqd->num_actuators - 1 || + bfqd->rq_in_driver[i] < bfqd->rq_in_driver[i+1])) { struct bfq_queue *bfqq = bfq_find_active_bfqq_for_actuator(bfqd, i);