Re: [RFC][PATCH 2/6] perf, arch: Rework perf_event_index()

From: Peter Zijlstra
Date: Mon Nov 21 2011 - 14:18:48 EST


On Mon, 2011-11-21 at 17:23 +0000, Will Deacon wrote:
> Hi Peter,
>
> On Mon, Nov 21, 2011 at 02:51:16PM +0000, Peter Zijlstra wrote:
> > Put the logic to compute the event index into a per pmu method. This
> > is required because the x86 rules are weird and wonderful and don't
> > match the capabilities of the current scheme.
> >
> > AFAIK only powerpc actually has a usable userspace read of the PMCs
> > but I'm not at all sure anybody actually used that.
> >
> > ARM looks like it cared, but I really wouldn't know, Will?
>
> It used to care, but it doesn't anymore. Feel free to make the offset 0 and
> use the (now) generic codepath.
>
> With that:
>
> Acked-by: Will Deacon <will.deacon@xxxxxxx>


But does ARM have a read PMU counter from userspace
instruction/capability?

Lacking that its all moot of course. If it does, it would be nice to
have an ARM version of patch 6.
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