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

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Message-ID: <87haevog75.fsf@tassilo.jf.intel.com>
Date:	Sun, 11 Aug 2013 18:23:10 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	Karim Yaghmour <karim.yaghmour@...rsys.com>
Cc:	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	mingo@...e.hu
Subject: Re: Reading perf counters at ftrace trace boundaries

Karim Yaghmour <karim.yaghmour@...rsys.com> writes:

> Wondering if there's a way for reading perf counters in the kernel. I'd
> like to read/record perf counters on ftrace function tracing
> entries/exits to provide a rundown of the value of various counters on
> function call boundaries.

KVM does it, see arch/x86/kvm/pmu.c. Essentially it would be doing RDPMC.

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

-Andi

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