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McKenney" Cc: LKML , Frederic Weisbecker , rcu , Uladzislau Rezki , Neeraj Upadhyay , Joel Fernandes , Giovanni Gherdovich Subject: [PATCH 0/9] rcu: Support for lazy callbacks on !CONFIG_RCU_NOCB_CPU Date: Wed, 31 May 2023 12:17:27 +0200 Message-Id: <20230531101736.12981-1-frederic@kernel.org> X-Mailer: git-send-email 2.40.1 MIME-Version: 1.0 X-Spam-Status: No, score=-7.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE 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?1767404948663180445?= X-GMAIL-MSGID: =?utf-8?q?1767404948663180445?= Hi, Here is a first attempt at providing support for lazy callbacks on non-offloaded CPUs. I have measured interesting results on my machine when it is mostly idle (just an idle ssh connection kept alive) with a gain of +10% idle time. This needs more serious testing though, especially to make sure that no performance regression is introduced. Also I have only mildly tested on NOCB (eg: no rcutorture yet), so I might have broken something. Finally it's also possible that the idle time improvement is due to me introducing a bug :) The patches 1-5 can be considered independently from the rest. Frederic Weisbecker (9): rcu: Assume IRQS disabled from rcu_report_dead() rcu: Use rcu_segcblist_segempty() instead of open coding it rcu: Rename jiffies_till_flush to jiffies_lazy_flush rcu: Introduce lazy queue's own qhimark rcu: Add rcutree.lazy_enabled boot parameter rcu/nocb: Rename was_alldone to was_pending rcu: Implement lazyness on the main segcblist level rcu: Make segcblist flags test strict rcu: Support lazy callbacks with CONFIG_RCU_NOCB=n .../admin-guide/kernel-parameters.txt | 5 + include/linux/rcu_segcblist.h | 13 +- kernel/rcu/Kconfig | 2 +- kernel/rcu/rcu.h | 8 +- kernel/rcu/rcu_segcblist.c | 44 ++- kernel/rcu/rcu_segcblist.h | 32 +- kernel/rcu/rcuscale.c | 6 +- kernel/rcu/tree.c | 272 +++++++++++++++-- kernel/rcu/tree.h | 9 +- kernel/rcu/tree_nocb.h | 285 +++++------------- 10 files changed, 425 insertions(+), 251 deletions(-)