On Sat, Oct 14, 2017 at 09:39:21AM -0600, Jens Axboe wrote:
> On 10/14/2017 03:22 AM, Ming Lei wrote:
> > Hi Jens,
> >
> > In Red Hat internal storage test wrt. blk-mq scheduler, we found that I/O
> > performance is much bad with mq-deadline, especially about sequential I/O
> > on some multi-queue
On Sat, Oct 14, 2017 at 07:38:29PM +0200, Oleksandr Natalenko wrote:
> Hi.
>
> By any chance, could this be backported to 4.14? I'm confused with "SCSI:
> allow to pass null rq to scsi_prep_state_check()" since it uses refactored
> flags.
>
> ===
> if (req && !(req->rq_flags & RQF_PREEMPT))
> =
Hi.
By any chance, could this be backported to 4.14? I'm confused with "SCSI:
allow to pass null rq to scsi_prep_state_check()" since it uses refactored
flags.
===
if (req && !(req->rq_flags & RQF_PREEMPT))
===
Is it safe to revert to REQ_PREEMPT here, or rq_flags should also be replaced
with
On 10/14/2017 03:22 AM, Ming Lei wrote:
> Hi Jens,
>
> In Red Hat internal storage test wrt. blk-mq scheduler, we found that I/O
> performance is much bad with mq-deadline, especially about sequential I/O
> on some multi-queue SCSI devcies(lpfc, qla2xxx, SRP...)
>
> Turns out one big issue causes
We need to iterate ctx starting from any ctx in round robin
way, so introduce this helper.
Reviewed-by: Omar Sandoval
Cc: Omar Sandoval
Signed-off-by: Ming Lei
---
include/linux/sbitmap.h | 64 -
1 file changed, 47 insertions(+), 17 deletions(-)
When hw queue is busy, we shouldn't take requests from
scheduler queue any more, otherwise it is difficult to do
IO merge.
This patch fixes the awful IO performance on some
SCSI devices(lpfc, qla2xxx, ...) when mq-deadline/kyber
is used by not taking requests if hw queue is busy.
Reviewed-by: Oma
There may be request in sw queue, and not fetched to domain queue
yet, so check it in kyber_has_work().
Signed-off-by: Ming Lei
---
block/kyber-iosched.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index f58cab82105b..94df3ce9
So that it becomes easy to support to dispatch from sw queue in the
following patch.
No functional change.
Reviewed-by: Bart Van Assche
Reviewed-by: Omar Sandoval
Suggested-by: Christoph Hellwig # for simplifying dispatch logic
Signed-off-by: Ming Lei
---
block/blk-mq-sched.c | 43 ++
SCSI devices use host-wide tagset, and the shared driver tag space is
often quite big. Meantime there is also queue depth for each lun(
.cmd_per_lun), which is often small, for example, on both lpfc and
qla2xxx, .cmd_per_lun is just 3.
So lots of requests may stay in sw queue, and we always flush
For SCSI devices, there is often per-request-queue depth, which need
to be respected before queuing one request.
The current blk-mq always dequeues request first, then calls .queue_rq()
to dispatch the request to lld. One obvious issue of this way is that I/O
merge may not be good, because when th
In the following patch, we will implement scsi_get_budget()
which need to call scsi_prep_state_check() when rq isn't
dequeued yet.
Signed-off-by: Ming Lei
---
drivers/scsi/scsi_lib.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/sc
We need to tell blk-mq for reserving resource before queuing
one request, so implement these two callbacks. Then blk-mq
can avoid to dequeue request earlier, and IO merge can
be improved a lot.
Signed-off-by: Ming Lei
---
drivers/scsi/scsi_lib.c | 75 ++---
Hi Jens,
In Red Hat internal storage test wrt. blk-mq scheduler, we found that I/O
performance is much bad with mq-deadline, especially about sequential I/O
on some multi-queue SCSI devcies(lpfc, qla2xxx, SRP...)
Turns out one big issue causes the performance regression: requests are
still dequeu
On Fri, Oct 13, 2017 at 11:16:12PM +, Bart Van Assche wrote:
> On Sat, 2017-10-14 at 02:05 +0800, Ming Lei wrote:
> > In the following patch, we will implement scsi_get_budget()
> > which need to call scsi_prep_state_check() when rq isn't
> > dequeued yet.
>
> My understanding is that this cha
On Fri, Oct 13, 2017 at 11:43:44PM +, Bart Van Assche wrote:
> On Sat, 2017-10-14 at 02:05 +0800, Ming Lei wrote:
> > @@ -89,19 +89,36 @@ static bool blk_mq_sched_restart_hctx(struct
> > blk_mq_hw_ctx *hctx)
> > return false;
> > }
> >
> > -static void blk_mq_do_dispatch_sched(struct bl
On Fri, Oct 13, 2017 at 02:23:07PM -0600, Jens Axboe wrote:
> On 10/13/2017 01:21 PM, Jens Axboe wrote:
> > On 10/13/2017 01:08 PM, Jens Axboe wrote:
> >> On 10/13/2017 12:05 PM, Ming Lei wrote:
> >>> Hi Jens,
> >>>
> >>> In Red Hat internal storage test wrt. blk-mq scheduler, we found that I/O
> >
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