From: Pavel Begunkov <asml.silence@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
io-uring@vger.kernel.org
Subject: Re: [PATCH] /dev/mem: nowait zero/null ops
Date: Wed, 8 Sep 2021 11:54:53 +0100 [thread overview]
Message-ID: <b03a27cd-1e5a-9444-c406-e15c52d2a066@gmail.com> (raw)
In-Reply-To: <YTiPoKc9GiG52DNd@kroah.com>
On 9/8/21 11:25 AM, Greg Kroah-Hartman wrote:
> On Wed, Sep 08, 2021 at 11:06:51AM +0100, Pavel Begunkov wrote:
>> Make read_iter_zero() to honor IOCB_NOWAIT, so /dev/zero can be
>> advertised as FMODE_NOWAIT. This helps subsystems like io_uring to use
>> it more effectively. Set FMODE_NOWAIT for /dev/null as well, it never
>> waits and therefore trivially meets the criteria.
>
> I do not understand, why would io_uring need to use /dev/zero
Not directly, users can issue I/O against it via io_uring.
> and how is this going to help anything?
For files not supporting nowait io_uring goes through a quite slow path.
> What workload does this help with?
Personally for me it's dumping output and benchmarking (not benchmarking
/dev/zero, of course). But I'd also expect any tool that may be using
it but rewritten with io_uring being able to normally use it without a
performance hit.
--
Pavel Begunkov
next prev parent reply other threads:[~2021-09-08 10:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-08 10:06 [PATCH] /dev/mem: nowait zero/null ops Pavel Begunkov
2021-09-08 10:25 ` Greg Kroah-Hartman
2021-09-08 10:54 ` Pavel Begunkov [this message]
2021-09-08 12:57 ` Jens Axboe
2021-09-08 13:07 ` Pavel Begunkov
2021-09-08 13:53 ` Jens Axboe
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