linux-kernel - Re: [RFC PATCH 0/3] perf: show package power consumption in perf

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Date:	Thu, 19 Aug 2010 11:28:17 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"Zhang, Rui" <rui.zhang@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"robert.richter@....com" <robert.richter@....com>,
	"acme@...hat.com" <acme@...hat.com>,
	"paulus@...ba.org" <paulus@...ba.org>,
	"dzickus@...hat.com" <dzickus@...hat.com>,
	"gorcunov@...il.com" <gorcunov@...il.com>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"Brown, Len" <lenb@...nel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>
Subject: Re: [RFC PATCH 0/3] perf: show package power consumption in perf

On Wed, 2010-08-18 at 20:41 +0800, Matt Fleming wrote:
> On Wed, Aug 18, 2010 at 02:25:29PM +0200, Peter Zijlstra wrote:
> > On Wed, 2010-08-18 at 15:59 +0800, Zhang Rui wrote:
> > > Hi, all,
> > > 
> > > RAPL(running average power limit) is a new feature which provides
> > > mechanisms to enforce power consumption limit, on some new processors.
> > > 
> > > Generally speaking, by using RAPL, OS can set a power budget in a
> > > certain time window, and let Hardware to throttle the processor
> > > P/T-state to meet this energy limitation.
> > > 
> > > RAPL also provides a new MSR, i.e. MSR_PKG_ENERGY_STATUS, which reports
> > > the total amount of energy consumed by the package.
> > > 
> > > I'm not sure if to support RAPL or not, but anyway, it sounds like a
> > > good idea to export the energy status in perf.
> > > 
> > > So a new perf pmu and event to show the package energy consumed is
> > > introduced in this patch.
> > > 
> > > Here is what I get after applying the three patches,
> > > 
> > > #./perf stat -e energy test
> > > Performance counter stats for 'test':
> > > 
> > > 	202	Joules cost by package
> > > 7.926001238	seconds time elapsed
> > > 
> > > 
> > > Note that this patch set is made based on Peter's perf-pmu branch,
> > > git://git.kernel.org/pub/scm/linux/kernel/git/peterz/linux-2.6-perf.git
> > >  which provides better interfaces to register/unregister a new pmu.
> > > 
> > > any comment are welcome. :)
> > 
> > 
> > Nice,.. however:
> > 
> >  - if it is a pure read-only counter without sampling support,
> >    expose it as such, don't fudge in the hrtimer stuff. Simply
> >    fail to create a sampling event.
> > 
> >    SH has the same problem for its 'normal' PMU, the solution is
> >    to use event groups, Matt was looking at adding support to
> >    perf-record for that, if creating a sampling event fails, fall
> >    back to {hrtimer, $event} groups.
> 
> I had a quick look over the patches and Peter is right - the group
> events stuff would probably fit quite well here. Unfortunately, due to
> holidays and things, I haven't been able to get them finished
> yet. I'll get on that ASAP.

Hi, Matt

What's the "group events stuff"?
Is there some discussion on LKML or elsewhere I can have a look at?

Thanks,
Lin Ming



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