* Re: [PATCH RESEND] block/mq-deadline: adjust the timeout period of the per_prio->dispatch
2025-09-26 2:38 [PATCH RESEND] block/mq-deadline: adjust the timeout period of the per_prio->dispatch chengkaitao
@ 2025-10-02 21:27 ` Jens Axboe
2025-10-03 4:17 ` Damien Le Moal
2025-10-03 4:19 ` Damien Le Moal
2 siblings, 0 replies; 4+ messages in thread
From: Jens Axboe @ 2025-10-02 21:27 UTC (permalink / raw)
To: chengkaitao; +Cc: linux-block, linux-kernel, chengkaitao, Damien Le Moal
On 9/25/25 8:38 PM, chengkaitao wrote:
> From: chengkaitao <chengkaitao@kylinos.cn>
>
> Reference function started_after()
> Before modification:
> Timeout for dispatch{read}: 9.5s
> started_after - 0.5s < latest_start - 10s
> 9.5s < latest_start - started_after
>
> Timeout for dispatch{write}: 5s
> started_after - 5s < latest_start - 10s
> 5s < latest_start - started_after
>
> At this point, write requests have higher priority than read requests.
>
> After modification:
> Timeout for dispatch{read/write}: 5s
> prio_aging_expire / 2 < latest_start - started_after
>
> Signed-off-by: chengkaitao <chengkaitao@kylinos.cn>
> ---
> block/mq-deadline.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/mq-deadline.c b/block/mq-deadline.c
> index b9b7cdf1d3c9..f311168f8dfe 100644
> --- a/block/mq-deadline.c
> +++ b/block/mq-deadline.c
> @@ -672,7 +672,8 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
>
> if (flags & BLK_MQ_INSERT_AT_HEAD) {
> list_add(&rq->queuelist, &per_prio->dispatch);
> - rq->fifo_time = jiffies;
> + rq->fifo_time = jiffies + dd->fifo_expire[data_dir]
> + - dd->prio_aging_expire / 2;
> } else {
> deadline_add_rq_rb(per_prio, rq);
>
Adding Damien as he's worked on mq-deadline the most recently.
--
Jens Axboe
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH RESEND] block/mq-deadline: adjust the timeout period of the per_prio->dispatch
2025-09-26 2:38 [PATCH RESEND] block/mq-deadline: adjust the timeout period of the per_prio->dispatch chengkaitao
2025-10-02 21:27 ` Jens Axboe
@ 2025-10-03 4:17 ` Damien Le Moal
2025-10-03 4:19 ` Damien Le Moal
2 siblings, 0 replies; 4+ messages in thread
From: Damien Le Moal @ 2025-10-03 4:17 UTC (permalink / raw)
To: chengkaitao, axboe; +Cc: linux-block, linux-kernel, chengkaitao
On 9/26/25 11:38, chengkaitao wrote:
> From: chengkaitao <chengkaitao@kylinos.cn>
>
> Reference function started_after()
What does this mean ?
> Before modification:
> Timeout for dispatch{read}: 9.5s
> started_after - 0.5s < latest_start - 10s
> 9.5s < latest_start - started_after
>
> Timeout for dispatch{write}: 5s
> started_after - 5s < latest_start - 10s
> 5s < latest_start - started_after
>
> At this point, write requests have higher priority than read requests.
>
> After modification:
> Timeout for dispatch{read/write}: 5s
> prio_aging_expire / 2 < latest_start - started_after
This is extremely hard to parse and understand. Can you please make full
sentences that explain what the problem is, and for your example, the starting
situation/state you are in ? E.g "If there are a lot of request inserted at
head, then ... Blah"
Also, in the title, s/timeout period/timeout
> Signed-off-by: chengkaitao <chengkaitao@kylinos.cn>
> ---
> block/mq-deadline.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/mq-deadline.c b/block/mq-deadline.c
> index b9b7cdf1d3c9..f311168f8dfe 100644
> --- a/block/mq-deadline.c
> +++ b/block/mq-deadline.c
> @@ -672,7 +672,8 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
>
> if (flags & BLK_MQ_INSERT_AT_HEAD) {
> list_add(&rq->queuelist, &per_prio->dispatch);
> - rq->fifo_time = jiffies;
> + rq->fifo_time = jiffies + dd->fifo_expire[data_dir]
> + - dd->prio_aging_expire / 2;
The request is inserted to the dispatch list directly here. So why do we need to
change the timeout to switch to fifo ? Your commit message does not explain that
at all, and I do not see a trivial explanation for it myself. Please clarify.
I suspect that you have a situation where you see a lot of requeue at head and
that completely skew the fifo/prio aging ? I am memrely guessing here. Please
resend your patch with a clear commit message, and also a comment for the change
above explaining what is being done.
> } else {
> deadline_add_rq_rb(per_prio, rq);
>
--
Damien Le Moal
Western Digital Research
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH RESEND] block/mq-deadline: adjust the timeout period of the per_prio->dispatch
2025-09-26 2:38 [PATCH RESEND] block/mq-deadline: adjust the timeout period of the per_prio->dispatch chengkaitao
2025-10-02 21:27 ` Jens Axboe
2025-10-03 4:17 ` Damien Le Moal
@ 2025-10-03 4:19 ` Damien Le Moal
2 siblings, 0 replies; 4+ messages in thread
From: Damien Le Moal @ 2025-10-03 4:19 UTC (permalink / raw)
To: chengkaitao, axboe; +Cc: linux-block, linux-kernel, chengkaitao
On 9/26/25 11:38, chengkaitao wrote:
> From: chengkaitao <chengkaitao@kylinos.cn>
>
> Reference function started_after()
> Before modification:
> Timeout for dispatch{read}: 9.5s
> started_after - 0.5s < latest_start - 10s
> 9.5s < latest_start - started_after
>
> Timeout for dispatch{write}: 5s
> started_after - 5s < latest_start - 10s
> 5s < latest_start - started_after
>
> At this point, write requests have higher priority than read requests.
>
> After modification:
> Timeout for dispatch{read/write}: 5s
> prio_aging_expire / 2 < latest_start - started_after
>
> Signed-off-by: chengkaitao <chengkaitao@kylinos.cn>
Also please write your name correctly here, separating first and last names with
a capital first letter for each (unless of course if this is your only
name/firstname, but still missing the capital letter).
> ---
> block/mq-deadline.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/mq-deadline.c b/block/mq-deadline.c
> index b9b7cdf1d3c9..f311168f8dfe 100644
> --- a/block/mq-deadline.c
> +++ b/block/mq-deadline.c
> @@ -672,7 +672,8 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
>
> if (flags & BLK_MQ_INSERT_AT_HEAD) {
> list_add(&rq->queuelist, &per_prio->dispatch);
> - rq->fifo_time = jiffies;
> + rq->fifo_time = jiffies + dd->fifo_expire[data_dir]
> + - dd->prio_aging_expire / 2;
> } else {
> deadline_add_rq_rb(per_prio, rq);
>
--
Damien Le Moal
Western Digital Research
^ permalink raw reply [flat|nested] 4+ messages in thread