linux-kernel - Re: [PATCH] fs: prefer read_iter over read and write

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Message-ID: <471e5654-49d7-9023-62b4-fc98483b1d89@kernel.dk>
Date:   Fri, 20 May 2022 16:18:06 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     David Laight <David.Laight@...LAB.COM>,
        "'Jason A. Donenfeld'" <Jason@...c4.com>
Cc:     "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fs: prefer read_iter over read and write_iter over write

On 5/20/22 4:08 PM, David Laight wrote:
>>    https://lore.kernel.org/lkml/Yoey+FOYO69lS5qP@zx2c4.com/
>>
>> The hope is that it eventually becomes faster... :-\
> 
> I suspect all the xxx_iter functions need optimising for
> the common case of a single buffer in userspace.
> 
> That also includes the code to read the iov[] from usespace.
> At the moment I think the 32bit compat code is actually
> faster than the native amd64 version!
> I've written some patches to speed that up.
> But the bigger improvements all hit massive changes
> to the ioring code.

Do you have a link to those patches? I can certainly help with the
io_uring side of things, and I have a genuine interest in improving the
core and getting the iter side up to snuff.

-- 
Jens Axboe