lkml.org 
[lkml]   [2005]   [Nov]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [Perfctr-devel] Re: Enabling RDPMC in user space by default
On Tue, Nov 29, 2005 at 01:43:11PM -0800, Nicholas Miell wrote:
> On Tue, 2005-11-29 at 19:13 +0100, Andi Kleen wrote:
> > > Where did you see that PMC0 (PERSEL0/PERFCTR0) can only be programmed
> > > to count cpu cycles (i.e. cpu_clk_unhalted)? As far as I can tell from
> > > the documentation, the 4 counters are symetrical and can measure
> > > any event that the processor offers.
> >
> > Linux NMI watchdog does that.
> >
> > All other perfctr users are supposed to keep their fingers away
> > from the watchdog (it looks like oprofile doesn't but not for much
> > longer ...)
>
> Why? Hardcoding PMC 0 to be a cycle counter seems to be a waste of a
> perfectly usable performance counter. What if I want to profile four
> things, none of them requiring a cycle count?

You won't then anymore. Providing a full replacement for RDTSC is
more important.

-Andi

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-11-29 22:54    [W:0.494 / U:0.904 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site