linux-kernel - Re: [GIT PULL] oprofile fixes for v2.6.40

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Message-ID: <20110530100956.GA17821@elte.hu>
Date:	Mon, 30 May 2011 12:09:56 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Robert Richter <robert.richter@....com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"oprofile-list@...ts.sourceforge.net" 
	<oprofile-list@...ts.sourceforge.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [GIT PULL] oprofile fixes for v2.6.40


* Robert Richter <robert.richter@....com> wrote:

> > But i really do not see how this can work. get_eilvt() twiddles 
> > the APIC LVT of this current CPU. Does IBS only activate on a 
> > single CPU? How will this LVT entry be cleared on deinit?
> 
> This is done on the current cpu to get the offset which is then 
> used on all cpus of the system. The actually per-core setup for ibs 
> is in op_amd_setup_ctrs(). Deinit is in op_amd_cpu_shutdown().

The way IBS is set up is not very obvious and atypical of existing 
preempt_*() patters. Might be worth adding a comment to the 
preempt_disable(), to unconfuse unsuspecting readers who are 
wondering about its oddness?

Anyway, i suspected that it was correctly working code so i pulled it 
and pushed it to Linus, it should all be in 3.0-rc1.

Thanks,

	Ingo
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