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

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Message-ID: <20110705103403.GN17941@sun>
Date:	Tue, 5 Jul 2011 14:34:03 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
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

On Tue, Jul 05, 2011 at 12:20:17PM +0200, Ingo Molnar wrote:
> 
> * Cyrill Gorcunov <gorcunov@...il.com> wrote:
...
> 
> So why don't we simply set this for all PERF_COUNT_HW_CPU_CYCLES 
> events in the P4 PMU driver? That would remove half of the patch 
> AFAICS.
> 
> Thanks,
> 
> 	Ingo

Unfortunately it doesn't solve the main issue -- nmi-watchdog events
and cpu clock events should be a separate events with non-intersected
ESCRs, otherwise nmi-watchdog and cpu-cycles can't operate simultaneously
like other PMUs does.

non-sleeping ticks use

	[P4_EVENT_EXECUTION_EVENT] = {
		.escr_msr	= { MSR_P4_CRU_ESCR2, MSR_P4_CRU_ESCR3 },
		.cntr		= { {12, 13, 16}, {14, 15, 17}
	},

while cpu-cycles

	[P4_EVENT_GLOBAL_POWER_EVENTS] = {
		.escr_msr	= { MSR_P4_FSB_ESCR0, MSR_P4_FSB_ESCR1 },
		.cntr		= { {0, -1, -1}, {2, -1, -1} },
	},

Note non-intersection of { MSR_P4_CRU_ESCR2, MSR_P4_CRU_ESCR3 } and
{ MSR_P4_FSB_ESCR0, MSR_P4_FSB_ESCR1 } here (together with counters
itselves pointed by .cntr).

	Cyrill
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