linux-kernel - Re: [PATCH next 0/3] iov: Optimise user copies

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Message-ID: <CAHk-=whs5oVkHMrNP=xkJP4Z4fObn=6Mz3fYp4wWMNQWtyjo9w@mail.gmail.com>
Date: Fri, 21 Mar 2025 16:35:52 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: David Laight <david.laight.linux@...il.com>
Cc: linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>, 
	David Howells <dhowells@...hat.com>, Matthew Wilcox <willy@...radead.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH next 0/3] iov: Optimise user copies

On Fri, 21 Mar 2025 at 15:46, David Laight <david.laight.linux@...il.com> wrote:
>
> The speculation barrier in access_ok() is expensive.
>
> The first patch removes the initial checks when reading the iovec[].
> The checks are repeated before the actual copy.
>
> The second patch uses 'user address masking' if supported.
>
> The third removes a lot of code for single entry iovec[].

Ack, except I'd really like to see numbers for things that claim to
remove expensive stuff.

But yeah, the patches look sane.

          Linus