linux-kernel - Re: perf_counters: page fault trace record

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Message-ID: <4A336700.3060309@linux.vnet.ibm.com>
Date:	Sat, 13 Jun 2009 01:44:48 -0700
From:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>
To:	Paul Mackerras <paulus@...ba.org>
CC:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: perf_counters: page fault trace record

Paul Mackerras wrote:
> Corey Ashford writes:
> 
>> One of the tools we are working on needs to be able to look not only at counts 
>> of page faults, but where they are occurring (ip and faulting page address).
>>
>> What would you think about adding a new bit to the config record, something like:
> 
> Can't you do what you need just using a page fault software counter
> with sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_ADDR and
> sample_period = 1?

I thought about that, but I was under the (incorrect?) impression that 
on Power, the PERF_SAMPLE_ADDR would be set by the value of the SDAR 
register, which wouldn't be correct for the case of a page fault.

I need to go look at the kernel code :)

- Corey

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