lkml.org 
[lkml]   [2010]   [Apr]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH V2 0/6][RFC] futex: FUTEX_LOCK with optional adaptive spinning
From
Date
On Tue, 2010-04-06 at 07:47 -0700, Ulrich Drepper wrote:
> On Tue, Apr 6, 2010 at 01:48, Peter Zijlstra <peterz@infradead.org>
> wrote:
> > try
> > spin
> > try
> > syscall
>
> This is available for a long time in the mutex implementation
> (PTHREAD_MUTEX_ADAPTIVE_NP mutex type). It hasn't show much
> improvement if any. There were some people demanding this support for
> as far as I know they are not using it now. This is adaptive
> spinning, learning from previous calls how long to wait. But it's
> still unguided. There is no way to get information like "the owner
> has been descheduled".

That's where the FUTEX_LOCK thing comes in, it does all those, the above
was a single spin loop to amortize the syscall overhead.

I wouldn't make it any more complex than a single pause ins, syscalls
are terribly cheap these days.



\
 
 \ /
  Last update: 2010-04-06 16:53    [W:0.090 / U:0.040 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site