linux-kernel - Re: [PATCH 0/26] oprofile: Performance counter multiplexing

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Message-ID: <20100308035143.GE20695@one.firstfloor.org>
Date:	Mon, 8 Mar 2010 04:51:43 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Robert Richter <robert.richter@....com>
Cc:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Paul Mackerras <paulus@...ba.org>,
	oprofile-list <oprofile-list@...ts.sourceforge.net>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 0/26] oprofile: Performance counter multiplexing

> the tests I run with oprofile do not indicate unreliable ring_buffer

Did you try it with callgraph mode? That seems to be worst.

> behavior. Maybe my use cases and loads are different. Can you describe
> a setup where this may happen for sure? What is the impact, do you

Seeing it on very busy 16 CPU and larger systems.

> have lost samples or inconsistent buffer data? Is the data loss in

There are a lot of lost samples, callgraphs are incomplete etc.

> kernel or user space? Also, I am not aware that the ring_buffer is

Not sure.

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