From: Andi Kleen <ak@suse.de>
To: Andrew Morton <akpm@osdl.org>
Cc: eranian@hpl.hp.com, Christoph Hellwig <hch@infradead.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] i386 add idle notifier
Date: Thu, 30 Nov 2006 00:21:41 +0100 [thread overview]
Message-ID: <200611300021.41497.ak@suse.de> (raw)
In-Reply-To: <20061129150544.ebd952f3.akpm@osdl.org>
> An alternative approach might be to change perfmon so that it works out
> whether it is being called by an idle thread
>
> if ((current->flags & PF_IDLE) && (other stuff to do with irqs?))
> return;
The problem is that the performance counters just keep running in the CPU.
Perfmon needs to do something actively to disable them.
Actually on x86 they usually stop in true idle state in hardware, but
they don't do in polling mode and it sometimes seems to depend on
the firmware. So it mostly would be for idle=poll
But if you do walk clock time profiling exactly because they stop
a profiler should account for this somehow. Otherwise the profiling time
doesn't add up to 100%
-Andi
next prev parent reply other threads:[~2006-11-29 23:22 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-11-29 16:25 [PATCH] i386 add idle notifier Stephane Eranian
2006-11-29 16:37 ` Andi Kleen
2006-11-29 16:41 ` [PATCH] i386 add idle notifier (take 2) Stephane Eranian
2006-11-29 17:09 ` [PATCH] i386 add idle notifier Christoph Hellwig
2006-11-29 21:09 ` Andrew Morton
2006-11-29 22:18 ` Stephane Eranian
2006-11-29 23:05 ` Andrew Morton
2006-11-29 23:15 ` Russell King
2006-11-29 23:21 ` Andi Kleen [this message]
2006-11-30 8:16 ` Stephane Eranian
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