From: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Omar Sandoval <osandov@fb.com>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: Re: [PATCH blktests 2/3] Add I/O scheduler tests for queue depth 1
Date: Mon, 9 May 2022 10:56:10 +0000 [thread overview]
Message-ID: <20220509105609.lqq6ffmyib3i4ojx@shindev> (raw)
In-Reply-To: <deaf359d-584f-f328-0b0a-1f3ce0e0937e@acm.org>
On Apr 28, 2022 / 12:52, Bart Van Assche wrote:
> On 4/27/22 23:27, Shinichiro Kawasaki wrote:
> > On Apr 27, 2022 / 14:31, Bart Van Assche wrote:
> > > Some block devices, e.g. USB sticks, only support queue depth 1. The
> > > QD=1 code paths do not get tested routinely. Hence add tests for the
> > > QD=1 use case.
> > >
> > > Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> >
> > I tried this new test case on recent Fedora kernel 5.16.20-200.fc35.x86_64 and
> > Intel Core i9 machine, then observed failure:
> >
> > $ sudo ./check block/032
> > block/032 (test I/O scheduler performance of null_blk with queue_depth 1) [failed]
> > bfq 679 vs 243: fail ... 679 vs 252: fail
> > kyber 542 vs 243: fail ... 551 vs 252: fail
> > mq-deadline 577 vs 243: fail ... 572 vs 252: fail
> > runtime 20.514s ... 20.660s
> > --- tests/block/032.out 2022-04-27 22:02:46.602861565 -0700
> > +++ /home/shin/kts/kernel-test-suite/src/blktests/results/nodev/block/032.out.bad2022-04-27 23:18:48.470170788 -0700
> > @@ -1,2 +1,2 @@
> > Running block/032
> > -Test complete
> > +Test failed
> >
> > I tried v5.18-rcX kernel versions and machines (QEMU or VMware) but the test
> > case failed on all of the trials. Do I miss anything to make the test case pass?
>
> Hi Shinichiro,
>
> The two tests added by this patch pass when using the legacy block layer
> (kernel v4.19) but not when using blk-mq. I see this as a (performance) bug
> in blk-mq. With blk-mq an excessive number of queue runs is triggered for
> QD=1 if multiple processes try to submit I/O concurrently.
Thanks. So we need the fix in blk-mq before we merge this test case to blktests.
--
Best Regards,
Shin'ichiro Kawasaki
next prev parent reply other threads:[~2022-05-09 10:56 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-27 21:31 [PATCH blktests 0/3] Add QD=1 and gap zone tests Bart Van Assche
2022-04-27 21:31 ` [PATCH blktests 1/3] Introduce the io_schedulers() function Bart Van Assche
2022-04-28 3:50 ` Shinichiro Kawasaki
2022-04-28 19:53 ` Bart Van Assche
2022-04-27 21:31 ` [PATCH blktests 2/3] Add I/O scheduler tests for queue depth 1 Bart Van Assche
2022-04-28 6:27 ` Shinichiro Kawasaki
2022-04-28 19:52 ` Bart Van Assche
2022-05-09 10:56 ` Shinichiro Kawasaki [this message]
2022-04-27 21:31 ` [PATCH blktests 3/3] tests/scsi: Add tests for SCSI devices with gap zones Bart Van Assche
2022-04-28 0:39 ` Shinichiro Kawasaki
2022-04-28 3:16 ` Bart Van Assche
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