Messages in this thread | | | Date | Tue, 29 Nov 2005 22:52:07 +0100 | From | Andi Kleen <> | Subject | Re: [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/
| |