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

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Date:	Fri, 8 Jul 2011 15:09:14 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Don Zickus <dzickus@...hat.com>,
	Stephane Eranian <eranian@...gle.com>,
	Lin Ming <ming.m.lin@...el.com>,
	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 Fri, Jul 08, 2011 at 02:49:06PM +0200, Ingo Molnar wrote:
> > 
> > * Cyrill Gorcunov <gorcunov@...il.com> wrote:
> > 
> > > > On P4 BUS_CYCLES would be able to co-exist with CPU_CYCLES so it 
> > > > will solve the P4 issue naturally as well.
> > > 
> > > i don't think it changes much, Ingo, if I change it to bus cycles I 
> > > still will have to setup nmi-watchdog event separately (but simply 
> > > with bus event).
> > 
> > You did not understand my point, my suggestion is to change this in 
> > kernel/watchdog.c:
> > 
> > static struct perf_event_attr wd_hw_attr = {
> >         .type           = PERF_TYPE_HARDWARE,
> >         .config         = PERF_COUNT_HW_CPU_CYCLES,
> > 
> > to:
> > 
> > static struct perf_event_attr wd_hw_attr = {
> >         .type           = PERF_TYPE_HARDWARE,
> >         .config         = PERF_COUNT_HW_BUS_CYCLES,
> > 
> > Thanks,
> > 
> > 	Ingo
> 
> Ah, I see. Ingo, if events alias patch I posted yesterday will do 
> the trick we will be able to simply drop all this hooks. So as only 
> Don (or someone) confirm the patch works I'll kill this mess.
> 
> Changing cpu-cycles to bus cycles will allow nmi-watchdog and perf 
> top co-exsist but it means perf bus-cycles won't work anymore with 
> active nmi-watchdog. So I think events aliases (again, if it work
> :) will be better for us, right?

Sure, being able to start two cycles events at once is better - 
assuming that those aliases work fine.

Thanks,

	Ingo
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