lkml.org 
[lkml]   [2014]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH 04/17] mm: gup: make get_user_pages_fast and __get_user_pages_fast latency conscious
From
On Fri, Oct 3, 2014 at 10:07 AM, Andrea Arcangeli <aarcange@redhat.com> wrote:
> This teaches gup_fast and __gup_fast to re-enable irqs and
> cond_resched() if possible every BATCH_PAGES.

This is disgusting.

Many (most?) __gup_fast() users just want a single page, and the
stupid overhead of the multi-page version is already unnecessary.
This just makes things much worse.

Quite frankly, we should make a single-page version of __gup_fast(),
and convert existign users to use that. After that, the few multi-page
users could have this extra latency control stuff.

And yes, the single-page version of get_user_pages_fast() is actually
latency-critical. shared futexes hit it hard, and yes, I've seen this
in profiles.

Linus


\
 
 \ /
  Last update: 2014-10-03 21:01    [W:0.364 / U:0.052 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site