linux-kernel - Re: Scheduler regression: Too frequent timer interrupts(?)

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Message-ID: <87vdp2qto0.fsf@basil.nowhere.org>
Date:	Sat, 18 Apr 2009 09:59:11 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	"Chris Friesen" <cfriesen@...tel.com>
Cc:	Christoph Lameter <cl@...ux.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: Scheduler regression: Too frequent timer interrupts(?)

"Chris Friesen" <cfriesen@...tel.com> writes:
>
> Given that we're talking about tens of usecs of duration, statistical
> sampling may not work all that well.

He could just use oprofile with a small period. The minimum period for
CPU_CLK_UNHALTED is 6000 (and it could be probably lowered by tweaking
the events) oprofile counters on x86 can be configured to only count
in ring 0 So you would get an entry every 6000 ring 0 cycles. That
should give a pretty good picture where the kernel is spending time.

-Andi


-- 
ak@...ux.intel.com -- Speaking for myself only.
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