Re: [RFC -tip] perf, x86: Add PERF_COUNT_HW_NMI_WATCHDOG event v2

From: Cyrill Gorcunov
Date: Tue Jun 21 2011 - 12:48:33 EST

On Tue, Jun 21, 2011 at 06:20:56PM +0200, Stephane Eranian wrote:
> Cyrill,
> [repost because of MIME crap]

I saw first as well, sorry for delay, my isp is broken today :/

> I admit I don't quite understand how this patch works around
> the limitation. In the end you are still going to program some cycle
> event into a P4 PMU register. So how it is going to free more counters
> for regular users?

The key here is that we use that named non-sleeping ticks (as oprofile
did) for nmi-watchdog and it allows us to free "cpu-cycles" counter for
user needs. Of course we pick up one counter for this but it doesn't intersect
with "cpu-cycles" counter (because counters are grouped and can count only
specified events in each group). Stepane, should I post more details?

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