linux-kernel - RE: [RFC,iov_iter v2 3/8] iov_iter: add copyin

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Message-ID: <8f65149b1d9a4a7f97f18df05a41f728@AcuMS.aculab.com>
Date:   Mon, 13 Jun 2022 15:31:51 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Joe Damato' <jdamato@...tly.com>
CC:     Alexander Viro <viro@...iv.linux.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC,iov_iter v2 3/8] iov_iter: add copyin_iovec helper

From: Joe Damato
> Sent: 13 June 2022 15:43
...
> > The additional costs of all the 'iovec' types is bad enough
> > already.
> 
> Do you have data you can share on this?

I was thinking of the performance drop noticed when (IIRC)
reads/writes of /dev/null were pushed through the iovec code.

But there is a lot of overhead code for the usual case
of a single user buffer being copied.

	David

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