diff mbox series

blk-mq: check on cpu id when there is only one ctx mapping

Message ID 20230531083828.8009-1-ed.tsai@mediatek.com
State New
Headers
Series blk-mq: check on cpu id when there is only one ctx mapping |

Commit Message

Ed Tsai (蔡宗軒) May 31, 2023, 8:38 a.m. UTC 
  commit f168420 ("blk-mq: don't redirect completion for hctx withs only
one ctx mapping") When nvme applies a 1:1 mapping of hctx and ctx, there
will be no remote request.

But for ufs, the submission and completion queues could be asymmetric.
(e.g. Multiple SQs share one CQ) Therefore, 1:1 mapping of hctx and
ctx won't complete request on the submission cpu. In this situation,
this nr_ctx check could violate the QUEUE_FLAG_SAME_FORCE, as a result,
check on cpu id when there is only one ctx mapping.

Signed-off-by: Ed Tsai <ed.tsai@mediatek.com>
Signed-off-by: Po-Wen Kao <powen.kao@mediatek.com>
---
 block/blk-mq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Stanley Jhu May 31, 2023, 9:04 a.m. UTC | #1 
On Wed, May 31, 2023 at 4:49 PM Ed Tsai <ed.tsai@mediatek.com> wrote:
>
> commit f168420 ("blk-mq: don't redirect completion for hctx withs only
> one ctx mapping") When nvme applies a 1:1 mapping of hctx and ctx, there
> will be no remote request.
>
> But for ufs, the submission and completion queues could be asymmetric.
> (e.g. Multiple SQs share one CQ) Therefore, 1:1 mapping of hctx and
> ctx won't complete request on the submission cpu. In this situation,
> this nr_ctx check could violate the QUEUE_FLAG_SAME_FORCE, as a result,
> check on cpu id when there is only one ctx mapping.
>
> Signed-off-by: Ed Tsai <ed.tsai@mediatek.com>
> Signed-off-by: Po-Wen Kao <powen.kao@mediatek.com>

Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Bart Van Assche June 11, 2023, 3:21 p.m. UTC | #2 
On 5/31/23 01:38, Ed Tsai wrote:
> commit f168420 ("blk-mq: don't redirect completion for hctx withs only
> one ctx mapping") When nvme applies a 1:1 mapping of hctx and ctx, there
> will be no remote request.

The above sentence is incomprehensible. Please make it comprehensible.

> Signed-off-by: Ed Tsai <ed.tsai@mediatek.com>
> Signed-off-by: Po-Wen Kao <powen.kao@mediatek.com>

This patch comes from Keith Busch. Why has his name not been mentioned? 
See also 
https://lore.kernel.org/linux-block/ZHY2TUrKVBj2xGE2@kbusch-mbp.dhcp.thefacebook.com/.

Bart.
diff mbox series

Patch

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 41f7e2b500bd..ecc30ebe9483 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1176,7 +1176,8 @@  bool blk_mq_complete_request_remote(struct request *rq)
 	 * or a polled request, always complete locally,
 	 * it's pointless to redirect the completion.
 	 */
-	if (rq->mq_hctx->nr_ctx == 1 ||
+	if ((rq->mq_hctx->nr_ctx == 1 &&
+	     rq->mq_ctx->cpu == raw_smp_processor_id()) ||
 		rq->cmd_flags & REQ_POLLED)
 		return false;