From: Mike Galbraith <bitbucket@online.de>
To: Andi Kleen <andi@firstfloor.org>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
Andi Kleen <ak@linux.intel.com>,
lenb@kernel.org, tglx@linutronix.de, peterz@infradead.org
Subject: Re: [PATCH] Trace idle entry and exit times
Date: Sat, 07 Dec 2013 09:22:24 +0100 [thread overview]
Message-ID: <1386404544.5673.88.camel@marge.simpson.net> (raw)
In-Reply-To: <20131207052029.GC21717@two.firstfloor.org>
On Sat, 2013-12-07 at 06:20 +0100, Andi Kleen wrote:
> On Sat, Dec 07, 2013 at 05:57:32AM +0100, Mike Galbraith wrote:
> > On Fri, 2013-12-06 at 16:46 -0800, Andi Kleen wrote:
> > > From: Andi Kleen <ak@linux.intel.com>
> > >
> > > This patch creates 4 new trace points: one at the beginning of idle,
> > > one before entering mwait, one after exiting mwait, and one after
> > > finishing the idle code. This is useful to trace down any
> > > additional latencies caused by the ever-growing idle code.
> > >
> > > Idle latencies are a common source of performance problems, so it's
> > > important to be able to measure them.
> >
> > You mean stuff like.. oh, say 60 cores doing zero work every 12ms
> > munching ~20% cpu?
>
> Well that one is obvious. I mean more the subtle problems.
Yeah, not subtle. SGI could use C2 as power supply stress tester.
-Mike
next prev parent reply other threads:[~2013-12-07 8:22 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-07 0:46 [PATCH] Trace idle entry and exit times Andi Kleen
2013-12-07 4:57 ` Mike Galbraith
2013-12-07 5:20 ` Andi Kleen
2013-12-07 8:22 ` Mike Galbraith [this message]
2013-12-07 17:29 ` Andi Kleen
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