lkml.org 
[lkml]   [2014]   [Jul]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC PATCH 0/5] futex: introduce an optimistic spinning futex
From
Date
On Mon, 2014-07-21 at 21:34 -0400, Steven Rostedt wrote:

> I was telling Robert that if futexes get optimistic spinning, he should
> reconsider their use of userspace spinlocks in favor of this, because
> I'm pretty sure that they will see a great improvement.

My (dated) experience with pgsql says you're likely right.

Once upon a time, preempting a userspace spinlock owner caused pgsql to
collapse into a quivering heap. The scheduler trying to hand the CPU
back to a preempted task instead of selecting what was strictly speaking
the most deserving task afterward (LAST_BUDDY) let pgsql+oltp scale nice
and flat instead of self destructing, but the root cause of collapse was
spinners lacking knowledge. With spin done in kernel, you can know
when spinning is a waste of perfectly good cycles.

-Mike



\
 
 \ /
  Last update: 2014-07-22 06:43    [W:0.152 / U:0.936 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site