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From:   Jens Axboe <axboe@kernel.dk>
To:     io-uring@vger.kernel.org, linux-kernel@vger.kernel.org,
        Andres Freund <andres@anarazel.de>
Cc:     Pavel Begunkov <asml.silence@gmail.com>
In-Reply-To: <20230707162007.194068-1-andres@anarazel.de>
References: <20230707162007.194068-1-andres@anarazel.de>
Subject: Re: [PATCH v1] io_uring: Use io_schedule* in cqring wait
Message-Id: <168875243541.1538686.6247556523906342367.b4-ty@kernel.dk>
Date:   Fri, 07 Jul 2023 11:53:55 -0600
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On Fri, 07 Jul 2023 09:20:07 -0700, Andres Freund wrote:
> I observed poor performance of io_uring compared to synchronous IO. That
> turns out to be caused by deeper CPU idle states entered with io_uring,
> due to io_uring using plain schedule(), whereas synchronous IO uses
> io_schedule().
> 
> The losses due to this are substantial. On my cascade lake workstation,
> t/io_uring from the fio repository e.g. yields regressions between 20%
> and 40% with the following command:
> ./t/io_uring -r 5 -X0 -d 1 -s 1 -c 1 -p 0 -S$use_sync -R 0 /mnt/t2/fio/write.0.0
> 
> [...]

Applied, thanks!

[1/1] io_uring: Use io_schedule* in cqring wait
      (no commit info)

Best regards,
-- 
Jens Axboe