linux-kernel - Re: [PATCH] perf: fix interrupt handler timing harness

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Date:	Mon, 8 Jul 2013 13:54:01 -0700
From:	Andi Kleen <ak@...ux.jf.intel.com>
To:	Dave Hansen <dave@...1.net>
Cc:	Stephane Eranian <eranian@...gle.com>,
	Dave Hansen <dave.hansen@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>, dave.hansen@...ux.jf.intel.com,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH] perf: fix interrupt handler timing harness

> I did a quite a bit of ftracing to look for spots inside the handler
> which were taking large amounts of time.  There were none.  The
> execution time was spread very evenly over the entire nmi handler.  It
> didn't appear to be any individual hot cachelines or doing something
> silly like sitting in a loop handling lots of PMU events.

In some cases callgraphs seemed to be quite expensive (large fraction
of the handler time)

-Andi
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