Re: [patch 02/14] tmpfs: fix regressions from wider use of ZERO_PAGE

Linus Torvalds
2022-05-04T20:40:28Z

On Wed, May 4, 2022 at 1:18 PM Borislav Petkov <bp@alien8.de> wrote:
>
> Zen3 has FSRM.

Sadly, I'm on Zen2 with my 3970X, and the Zen 3 threadrippers seem to
be basically impossible to get.

> So below's the git test suite with clear_user on Zen3. It creates a lot
> of processes so we get to clear_user a bunch and that's the inlined rep
> movsb.

Oh, the clear_user() in the ELF loader? I wouldn't have expected that
to be noticeable.

Now, clear_page() is *very* noticeable, but that has its own special
magic and doesn't use clear_user().

Maybe there is some other clear_user() case I never thought of. My dim
memories of profiles definitely had copy_to_user, clear_page and
copy_page being some of the top copy loops.

Linus