From: Matthew Wilcox <willy@infradead.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: David Laight <David.Laight@aculab.com>,
"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] eventfd: convert to using ->write_iter()
Date: Mon, 3 May 2021 19:02:07 +0100 [thread overview]
Message-ID: <20210503180207.GD1847222@casper.infradead.org> (raw)
In-Reply-To: <7caa3703-af14-2ff6-e409-77284da11e1f@kernel.dk>
On Mon, May 03, 2021 at 11:57:08AM -0600, Jens Axboe wrote:
> On 5/3/21 10:12 AM, David Laight wrote:
> > From: Jens Axboe
> >> Sent: 03 May 2021 15:58
> >>
> >> Had a report on writing to eventfd with io_uring is slower than it
> >> should be, and it's the usual case of if a file type doesn't support
> >> ->write_iter(), then io_uring cannot rely on IOCB_NOWAIT being honored
> >> alongside O_NONBLOCK for whether or not this is a non-blocking write
> >> attempt. That means io_uring will punt the operation to an io thread,
> >> which will slow us down unnecessarily.
> >>
> >> Convert eventfd to using fops->write_iter() instead of fops->write().
> >
> > Won't this have a measurable performance degradation on normal
> > code that does write(event_fd, &one, 4);
>
> If ->write_iter() or ->read_iter() is much slower than the non-iov
> versions, then I think we have generic issues that should be solved.
We do!
https://lore.kernel.org/linux-fsdevel/20210107151125.GB5270@casper.infradead.org/
is one thread on it. There have been others.
> That should not be a consideration, since the non-iov ones are
> legacy and should not be adopted in new code.
>
> --
> Jens Axboe
>
next prev parent reply other threads:[~2021-05-03 18:03 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-03 14:57 [PATCH] eventfd: convert to using ->write_iter() Jens Axboe
2021-05-03 16:12 ` David Laight
2021-05-03 17:57 ` Jens Axboe
2021-05-03 18:02 ` Matthew Wilcox [this message]
2021-05-03 18:05 ` Jens Axboe
2021-05-04 8:07 ` David Laight
2021-05-09 13:22 ` [eventfd] cd8a8dd187: WARNING:at_include/linux/thread_info.h:#eventfd_write kernel test robot
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