lkml.org 
[lkml]   [2013]   [Sep]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: perf_event: rdpmc self-monitoring overhead issue
On Mon, 2 Sep 2013, Stephane Eranian wrote:

> On Mon, Sep 2, 2013 at 4:50 AM, Andi Kleen <andi@firstfloor.org> wrote:
> > Stephane Eranian <eranian@googlemail.com> writes:
> >
> >> I don't see a flag in mmap() to fault it in immediately.
> >
> > MAP_PRESENT
> >
> I could not find this constant defined anywhere in the kernel source tree
> nor in /usr/include. Are you sure of the name?

I assume he means MAP_POPULATE

which does improve things, from ~3000 cycles to ~219 cycles but that's
still more overhead than the ~130 or so you get by manually touching the
page first.

Vince



\
 
 \ /
  Last update: 2013-09-02 15:41    [W:0.056 / U:0.680 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site