lkml.org 
[lkml]   [2017]   [Oct]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH V10 0/8] blk-mq-sched: improve sequential I/O performance
Date
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 cmd_flags?

Thanks.

On sobota 14. října 2017 11:22:24 CEST 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 the performance regression: requests are
> still dequeued from sw queue/scheduler queue even when ldd's queue is
> busy, so I/O merge becomes quite difficult to make, then sequential IO
> performance degrades a lot.
>
> This issue becomes one of mains reasons for reverting default SCSI_MQ
> in V4.13.
>
> This 8 patches improve this situation, and brings back performance loss.
>
> With this change, SCSI-MQ sequential I/O performance is improved much, Paolo
> reported that mq-deadline performance improved much[2] in his dbench test
> wrt V2. Also performance improvement on lpfc/qla2xx was observed with
> V1.[1]
>
> [1] http://marc.info/?l=linux-block&m=150151989915776&w=2
> [2] https://marc.info/?l=linux-block&m=150217980602843&w=2
>
> gitweb:
> https://github.com/ming1/linux/commits/
blk_mq_improve_scsi_mpath_perf_V10_p
> art1
>
> V10:
> - fix hang with kyber used
> - address comments from Bart
>
> V9:
> - change title of patch1
> - rename blk_mq_get_budget() as blk_mq_get_dispatch_budget()
> - make check on .get_budget/.put_budget cleaner
> - all are suggested by Jens, thank for review
>
> V8:
> - introduce helper of blk_mq_get_budget
> - handle failure path of get_budget
>
> V7:
> - introduce .get_budget/.put_budget, and IO merge gets improved
> compared with V6, and in theory this approach is better than the way
> taken in block legacy
>
> - drop patch of 'blk-mq-sched: don't dequeue request until all in
> ->dispatch are flushed'
>
> V6:
> - address comments from Christoph
> - drop the 1st patch which changes blk_mq_request_bypass_insert(),
> which should belong to dm-mpath's improvement
> - move ' blk-mq-sched: move actual dispatching into one helper'
> as 2nd patch, and use the introduced helper to simplify dispatch
> logic
> - merge two previous patches into one for improving dispatch from sw
queue
> - make comment/commit log line width as ~70, as suggested by
> Christoph
>
> V5:
> - address some comments from Omar
> - add Tested-by & Reveiewed-by tag
> - use direct issue for blk_mq_request_bypass_insert(), and
> start to consider to improve sequential I/O for dm-mpath
> - only include part 1(the original patch 1 ~ 6), as suggested
> by Omar
>
> V4:
> - add Reviewed-by tag
> - some trival change: typo fix in commit log or comment,
> variable name, no actual functional change
>
> V3:
> - totally round robin for picking req from ctx, as suggested
> by Bart
> - remove one local variable in __sbitmap_for_each_set()
> - drop patches of single dispatch list, which can improve
> performance on mq-deadline, but cause a bit degrade on
> none because all hctxs need to be checked after ->dispatch
> is flushed. Will post it again once it is mature.
> - rebase on v4.13-rc6 with block for-next
>
> V2:
> - dequeue request from sw queues in round roubin's style
> as suggested by Bart, and introduces one helper in sbitmap
> for this purpose
> - improve bio merge via hash table from sw queue
> - add comments about using DISPATCH_BUSY state in lockless way,
> simplifying handling on busy state,
> - hold ctx->lock when clearing ctx busy bit as suggested
> by Bart
>
>
> Ming Lei (8):
> blk-mq-sched: dispatch from scheduler only after progress is made on
> ->dispatch
> blk-mq-sched: move actual dispatching into one helper
> sbitmap: introduce __sbitmap_for_each_set()
> block: kyber: check if there is request in ctx in kyber_has_work()
> blk-mq: introduce .get_budget and .put_budget in blk_mq_ops
> blk-mq-sched: improve dispatching from sw queue
> SCSI: allow to pass null rq to scsi_prep_state_check()
> SCSI: implement .get_budget and .put_budget for blk-mq
>
> block/blk-mq-sched.c | 148
> +++++++++++++++++++++++++++++++++++++++++------- block/blk-mq-sched.h |
> 2 +-
> block/blk-mq.c | 82 +++++++++++++++++++++++++--
> block/blk-mq.h | 22 ++++++-
> block/kyber-iosched.c | 2 +-
> drivers/scsi/scsi_lib.c | 79 ++++++++++++++++++--------
> include/linux/blk-mq.h | 13 +++++
> include/linux/sbitmap.h | 64 +++++++++++++++------
> 8 files changed, 342 insertions(+), 70 deletions(-)


\
 
 \ /
  Last update: 2017-10-14 19:39    [W:0.047 / U:50.020 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site