From: Bart Van Assche <bvanassche@acm.org>
To: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
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: Thu, 28 Apr 2022 12:52:41 -0700 [thread overview]
Message-ID: <deaf359d-584f-f328-0b0a-1f3ce0e0937e@acm.org> (raw)
In-Reply-To: <20220428062659.udpifr26qgsqfysh@fedora>
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,
Bart.
next prev parent reply other threads:[~2022-04-28 19:52 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 [this message]
2022-05-09 10:56 ` Shinichiro Kawasaki
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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