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From: Kashyap Desai <kashyap.desai@broadcom.com>
References: <20180702093600.10315-1-ming.lei@redhat.com> <1530531681.8954.1.camel@redhat.com>
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Date: Mon, 2 Jul 2018 17:59:47 +0530
Message-ID: <2f75692a43952064c238a6aa070b0bf6@mail.gmail.com>
Subject: RE: [PATCH V3 0/3] blk-mq: improve IO perf in case of none io sched
To: Laurence Oberman <loberman@redhat.com>, Ming Lei <ming.lei@redhat.com>,
	Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, Omar Sandoval <osandov@fb.com>,
	Christoph Hellwig <hch@lst.de>, Bart Van Assche <bart.vanassche@wdc.com>, Hannes Reinecke <hare@suse.de>
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List-ID: <linux-block@vger.kernel.org>

> -----Original Message-----
> From: Laurence Oberman [mailto:loberman@redhat.com]
> Sent: Monday, July 2, 2018 5:11 PM
> To: Ming Lei; Jens Axboe
> Cc: linux-block@vger.kernel.org; Kashyap Desai; Omar Sandoval; Christoph
> Hellwig; Bart Van Assche; Hannes Reinecke
> Subject: Re: [PATCH V3 0/3] blk-mq: improve IO perf in case of none io
> sched
>
> On Mon, 2018-07-02 at 17:35 +0800, Ming Lei wrote:
> > Hi,
> >
> > The 1st 2 patch improves ctx->lock uses, and it is observed that IOPS
> > may be improved by ~5% in rand IO test on MegaRaid SAS run by
> > Kashyap.
> >
> > The 3rd patch fixes rand IO performance regression on MegaRaid SAS
> > test, still reported by Kashyap.
> >
> > V3:
> > 	- export dispatch busy from debugfs as suggested by Jens
> > 	- add comment on blk_mq_update_hctx_busy() as suggested by
> > Christoph
> >
> > V2:
> > 	- fix list corruption in patch 1/3
> >
> >
> > Ming Lei (3):
> >   blk-mq: use list_splice_tail_init() to insert requests
> >   blk-mq: only attempt to merge bio if there is rq in sw queue
> >   blk-mq: dequeue request one by one from sw queue iff hctx is busy
>
>
> >
> >  block/blk-mq-debugfs.c |  9 +++++++++
> >  block/blk-mq-sched.c   | 14 ++++----------
> >  block/blk-mq.c         | 44 ++++++++++++++++++++++++++++++++++++--
> > ------
> >  include/linux/blk-mq.h |  3 ++-
> >  4 files changed, 51 insertions(+), 19 deletions(-)
> >
> > Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> > Cc: Laurence Oberman <loberman@redhat.com>
> > Cc: Omar Sandoval <osandov@fb.com>
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: Bart Van Assche <bart.vanassche@wdc.com>
> > Cc: Hannes Reinecke <hare@suse.de>
> >
>
> Thanks Ming, I repaired my MSA50 shelf so will functional test.
> I have 6 SSD drives working in there now.
> I know its already been tested by Kashyap.

Performance is back to 1.6M IOPS which was earlier 1.3M IOPs on SSD based VD
@MegaRaid controller setup.

Tested-by: Kashyap Desai <kashyap.desai@broadcom.com>

>
> Regards
> Laurence