From: Liu Song <liusong@linux.alibaba.com>

High-performance NVMe devices usually support a large hw queue, which
ensures a 1:1 mapping of hctx and ctx. In this case there will be no
remote request, so we don't need to care about it.

Signed-off-by: Liu Song <liusong@linux.alibaba.com>
---
 block/blk-mq.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index c11949d..9626ea1 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1093,10 +1093,12 @@ bool blk_mq_complete_request_remote(struct request *rq)
 	WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
 
 	/*
-	 * For a polled request, always complete locally, it's pointless
-	 * to redirect the completion.
+	 * For request which hctx has only one ctx mapping,
+	 * or a polled request, always complete locally,
+	 * it's pointless to redirect the completion.
 	 */
-	if (rq->cmd_flags & REQ_POLLED)
+	if (rq->mq_hctx->nr_ctx == 1 ||
+		rq->cmd_flags & REQ_POLLED)
 		return false;
 
 	if (blk_mq_complete_need_ipi(rq)) {
-- 
1.8.3.1

On Wed, 21 Sep 2022 11:32:03 +0800, Liu Song wrote:
> From: Liu Song <liusong@linux.alibaba.com>
> 
> High-performance NVMe devices usually support a large hw queue, which
> ensures a 1:1 mapping of hctx and ctx. In this case there will be no
> remote request, so we don't need to care about it.
> 
> 
> [...]

Applied, thanks!

[1/1] blk-mq: hctx has only one ctx mapping is no need to redirect the completion
      commit: f168420c62e7a106961f2489a89f6ade84fe3f27

Best regards,
-- 
Jens Axboe

On Wed, Sep 21, 2022 at 11:32:03AM +0800, Liu Song wrote:
> From: Liu Song <liusong@linux.alibaba.com>
> 
> High-performance NVMe devices usually support a large hw queue, which

a larger number of?

>  	/*
> -	 * For a polled request, always complete locally, it's pointless
> -	 * to redirect the completion.
> +	 * For request which hctx has only one ctx mapping,
> +	 * or a polled request, always complete locally,
> +	 * it's pointless to redirect the completion.
>  	 */
> -	if (rq->cmd_flags & REQ_POLLED)
> +	if (rq->mq_hctx->nr_ctx == 1 ||
> +		rq->cmd_flags & REQ_POLLED)

Some very odd comment formatting and and indentation here.

On 2022/9/22 14:20, Christoph Hellwig wrote:

> On Wed, Sep 21, 2022 at 11:32:03AM +0800, Liu Song wrote:
>> From: Liu Song <liusong@linux.alibaba.com>
>>
>> High-performance NVMe devices usually support a large hw queue, which
> a larger number of?
>
>>   	/*
>> -	 * For a polled request, always complete locally, it's pointless
>> -	 * to redirect the completion.
>> +	 * For request which hctx has only one ctx mapping,
>> +	 * or a polled request, always complete locally,
>> +	 * it's pointless to redirect the completion.
>>   	 */
>> -	if (rq->cmd_flags & REQ_POLLED)
>> +	if (rq->mq_hctx->nr_ctx == 1 ||
>> +		rq->cmd_flags & REQ_POLLED)
> Some very odd comment formatting and and indentation here.

Thanks, I will issue a V2 patch as suggested.

From: Liu Song <liusong@linux.alibaba.com>

High-performance NVMe devices usually support a larger number of hw queue,
which ensures a 1:1 mapping of hctx and ctx. In this case there will be no
remote request, so we don't need to care about it.

Signed-off-by: Liu Song <liusong@linux.alibaba.com>
---
 block/blk-mq.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index c11949d..7f9be13 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1093,10 +1093,11 @@ bool blk_mq_complete_request_remote(struct request *rq)
 	WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
 
 	/*
-	 * For a polled request, always complete locally, it's pointless
-	 * to redirect the completion.
+	 * If the request's hctx has only one ctx mapping,
+	 * or is a polled request, both always complete locally,
+	 * it's pointless to redirect the completion.
 	 */
-	if (rq->cmd_flags & REQ_POLLED)
+	if (rq->mq_hctx->nr_ctx == 1 || rq->cmd_flags & REQ_POLLED)
 		return false;
 
 	if (blk_mq_complete_need_ipi(rq)) {
-- 
1.8.3.1