linux-kernel - Re: Reading perf counters at ftrace trace boundaries

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Message-ID: <52083CB4.2030308@opersys.com>
Date:	Sun, 11 Aug 2013 22:39:00 -0300
From:	Karim Yaghmour <karim.yaghmour@...rsys.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	mingo@...e.hu
Subject: Re: Reading perf counters at ftrace trace boundaries


On 13-08-11 10:23 PM, Andi Kleen wrote:
> KVM does it, see arch/x86/kvm/pmu.c. Essentially it would be doing RDPMC.

Thx for the pointer, appreciated.

> But the overhead will be likely very high, some sampling approach
> is likely better.

Indeed. It doesn't actually have to be at every single ftrace
begin/exit. But possibly starting with some kind of every nth and then
drilling down as the culprit is incrementally singled-out.

-- 
Karim Yaghmour
CEO - Opersys inc. / www.opersys.com
http://twitter.com/karimyaghmour

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