Re: perf: p6 PMU working by accident, should we fix it and KNC?
From: Peter Zijlstra
Date: Fri Oct 19 2012 - 10:08:35 EST
On Wed, 2012-10-17 at 11:35 -0400, Vince Weaver wrote:
> This is by accident; it looks like the code does
> val |= ARCH_PERFMON_EVENTSEL_ENABLE;
> in p6_pmu_disable_event() so that events are never truly disabled
> (is this a bug? should it be &=~ instead?).
I think that's on purpose.. from what I can remember p6 only has a
single EN bit (on PMC0) that acts for both counters. So what I did was
treat that as a global enable/disable (which it is) and did the local
enable/disable by using the NOP events.
There really might be bugs in there, its not like I use this class of
hardware very frequently (nor do anybody much it seems).
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