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From: Dmitry Shulyak <[email protected]>
To: Jens Axboe <[email protected]>
Cc: [email protected]
Subject: Re: Large number of empty reads on 5.9-rc2 under moderate load
Date: Tue, 25 Aug 2020 17:14:57 +0300	[thread overview]
Message-ID: <CAF-ewDrtgSpoannR9HOw-pLKCS3j-dYeoEHJ8c4pG=abfLaRuA@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>

I was doing readv with the same tool that i shared earlier:
go test ./fs -run=xx -bench=BenchmarkReadAt/os_5 -benchtime=8000000x -cpu=256

On 5.8.3 it is consistently > 100 mb/s, on 5.9-rc2 ~50 mb/s on my device.
with uring i was getting > 250 mb/s, and now ~70 mb/s.

double checked if there is any difference with writev, and i don't see any.


On Tue, 25 Aug 2020 at 16:39, Jens Axboe <[email protected]> wrote:
>
> On 8/25/20 2:52 AM, Dmitry Shulyak wrote:
> > this patch fixes the issue with 0 reads. there seems to be a
> > regression that is not specific to uring,
> > regular syscall reads slowed down noticeably.
>
> Do you have a test case? Related to specific system calls, or just
> overall? My initial suspicion would be Yet Another one of the
> security fixes...
>
> --
> Jens Axboe
>

      reply	other threads:[~2020-08-25 14:15 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-24 10:40 Large number of empty reads on 5.9-rc2 under moderate load Dmitry Shulyak
2020-08-24 10:46 ` Jens Axboe
2020-08-24 11:09   ` Dmitry Shulyak
2020-08-24 14:06     ` Jens Axboe
2020-08-24 14:45       ` Jens Axboe
2020-08-24 15:33         ` Dmitry Shulyak
2020-08-24 16:10           ` Jens Axboe
2020-08-24 16:13             ` Dmitry Shulyak
2020-08-24 16:18               ` Jens Axboe
2020-08-24 17:44                 ` Jens Axboe
2020-08-25  8:52                   ` Dmitry Shulyak
2020-08-25 13:39                     ` Jens Axboe
2020-08-25 14:14                       ` Dmitry Shulyak [this message]

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