linux-kernel - Re: [PATCH -tip, final] perf, x86: Add hw_watchdog_set

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Message-ID: <20110705112002.GA15654@elte.hu>
Date:	Tue, 5 Jul 2011 13:20:02 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Don Zickus <dzickus@...hat.com>,
	Stephane Eranian <eranian@...gle.com>,
	Lin Ming <ming.m.lin@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -tip, final] perf, x86: Add hw_watchdog_set_attr() in a
 sake of nmi-watchdog on P4


* Cyrill Gorcunov <gorcunov@...il.com> wrote:

> On Tue, Jul 05, 2011 at 12:59:59PM +0200, Ingo Molnar wrote:
> ...
> > 
> > are 'non-sleeping ticks' non-halted cycles - i.e. cycles that 
> > always count with CPU frequency and can thus be used for periodic 
> > frequencies?
> 
> Yes, I think so (btw, as far as I remember oprofile does the same 
> 'threshold' gaming for nmi-watchdog).

But the NMI watchdog does not need a constant frequency event - it 
can use unhalted cycles just fine. Why does it need unhalted cycles 
on P4?

Thanks,

	Ingo
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