From: Andi Kleen <ak@suse.de>
To: eranian@hpl.hp.com
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH 10/17] 2.6.17.1 perfmon2 patch for review: PMU context switch
Date: Fri, 30 Jun 2006 15:41:22 +0200 [thread overview]
Message-ID: <200606301541.22928.ak@suse.de> (raw)
In-Reply-To: <20060630132901.GB22381@frankl.hpl.hp.com>
> So why do we need care about context switch in cpu-wide mode?
> It is because we support a mode where the idle thread is excluded
> from cpu-wide monitoring. This is very useful to distinguish
> 'useful kernel work' from 'idle'.
I don't quite see the point because on x86 the PMU doesn't run
during C states anyways. So you get idle excluded automatically.
And on the other hand a lot of people especially want idle
accounting too and boot with idle=poll. Your explicit
code would likely defeat that.
> As you realize, that means
> that we need to turn off when the idle thread is context switched
> in and turn it back on when it is switched off.
Also x86-64 has idle notifiers for this if you really wanted
to do it properly.
-Andi
next prev parent reply other threads:[~2006-06-30 13:41 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-06-23 9:13 [PATCH 10/17] 2.6.17.1 perfmon2 patch for review: PMU context switch Stephane Eranian
2006-06-30 12:27 ` Andi Kleen
2006-06-30 12:36 ` Stephane Eranian
2006-06-30 12:59 ` Andi Kleen
2006-06-30 13:29 ` Stephane Eranian
2006-06-30 13:41 ` Andi Kleen [this message]
2006-06-30 14:12 ` Stephane Eranian
2006-06-30 14:33 ` Andi Kleen
2006-06-30 16:02 ` Stephane Eranian
2006-06-30 17:08 ` Andi Kleen
2006-06-30 20:47 ` Stephane Eranian
2006-07-03 9:49 ` Stephane Eranian
2006-07-03 19:25 ` Andi Kleen
2006-07-03 19:22 ` Stephane Eranian
2006-07-03 19:36 ` Andi Kleen
-- strict thread matches above, loose matches on Subject: below --
2006-06-30 18:33 Chuck Ebbert
2006-06-30 18:42 ` Andi Kleen
2006-06-30 18:43 ` Stephane Eranian
2006-06-30 20:40 ` Stephane Eranian
2006-06-30 19:17 Chuck Ebbert
2006-06-30 19:37 ` Andi Kleen
2006-07-01 15:21 Chuck Ebbert
2006-07-04 15:28 ` Stephane Eranian
2006-07-06 17:30 Chuck Ebbert
2006-07-06 20:16 ` Stephane Eranian
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