From: Dmitry Shulyak <yashulyak@gmail.com>
To: io-uring@vger.kernel.org
Subject: Re: Very low write throughput on file opened with O_SYNC/O_DSYNC
Date: Mon, 17 Aug 2020 14:58:12 +0300 [thread overview]
Message-ID: <CAF-ewDq24YTjjH2E52dMU3+NZn2dc8O0cEQm=zSLN7Zbc17uLQ@mail.gmail.com> (raw)
In-Reply-To: <CAF-ewDrOHDxpSAm8Or37m-k5K4u+b3H2YwnA-KpkFuVa+1vBOw@mail.gmail.com>
Forgot to mention, that this is on 5.7.12, with writev/read during operations.
On Mon, 17 Aug 2020 at 14:46, Dmitry Shulyak <yashulyak@gmail.com> wrote:
>
> Hi everyone,
>
> I noticed in iotop that all writes are executed by the same thread
> (io_wqe_worker-0). This is a significant problem if I am using files
> with mentioned flags. Not the case with reads, requests are
> multiplexed over many threads (note the different name
> io_wqe_worker-1). The problem is not specific to O_SYNC, in the
> general case I can get higher throughput with thread pool and regular
> system calls, but specifically with O_SYNC the throughput is the same
> as if I were using a single thread for writing.
>
> The setup is always the same, ring per thread with shared workers pool
> (IORING_SETUP_ATTACH_WQ), and high submission rate. Also, it is
> possible to get around this performance issue by using separate worker
> pools, but then I have to load balance workload between many rings for
> perf gains.
>
> I thought that it may have something to do with the IOSQE_ASYNC flag,
> but setting it had no effect.
>
> Is it expected behavior? Are there any other solutions, except
> creating many rings with isolated worker pools?
next prev parent reply other threads:[~2020-08-17 11:58 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-17 11:46 Very low write throughput on file opened with O_SYNC/O_DSYNC Dmitry Shulyak
2020-08-17 11:58 ` Dmitry Shulyak [this message]
2020-08-17 14:29 ` Jens Axboe
2020-08-17 15:49 ` Dmitry Shulyak
2020-08-17 16:17 ` Jens Axboe
2020-08-18 16:09 ` Dmitry Shulyak
2020-08-18 16:42 ` Jens Axboe
2020-08-19 7:55 ` Dmitry Shulyak
2020-08-21 13:43 ` Dmitry Shulyak
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