linux-kernel - Re: [patch 05/24] perfmon: X86 generic code (x86)

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Message-Id: <20081127.034247.72331360.davem@davemloft.net>
Date:	Thu, 27 Nov 2008 03:42:47 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	eranian@...il.com, eranian@...glemail.com
Cc:	andi@...stfloor.org, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	mingo@...e.hu, x86@...nel.org, sfr@...b.auug.org.au
Subject: Re: [patch 05/24] perfmon: X86 generic code (x86)

From: "stephane eranian" <eranian@...glemail.com>
Date: Thu, 27 Nov 2008 12:35:54 +0100

> I am still wondering how Oprofile handles the case where multiple
> processes or threads access the same file descriptor.

There's only one profiling buffer active on a given cpu,
so it's pure per-cpu value insertion.

In any event I think that NMI profiling is a must, especially
for the kernel.  You get total unusable crap otherwise.  I
just learned this the hard way having gotten an NMI'ish scheme
working on sparc64 just the other day.
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