linux-kernel - Re: [PATCH 1/6] perf_counter: move the event overflow output bits to record

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Message-ID: <49D5BB05.2030700@linux.vnet.ibm.com>
Date:	Fri, 03 Apr 2009 00:30:13 -0700
From:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] perf_counter: move the event overflow output bits
 to record_type

Peter Zijlstra wrote:
> On Thu, 2009-04-02 at 16:27 -0700, Corey Ashford wrote:
>> Whoops, nevermind.
>>
>> My misunderstanding on this one.  This enum is used for event type, not 
>> the record_type, and as such is makes sense for there to be exclusive 
>> mmap and munmap event records.
>>
>> Thinking about this a bit, I'm guessing that the idea is to track the 
>> loading and unloading of shared objects which uses mmap and munmap, so 
>> that that the ip can be related to a particular object that was mapped 
>> in at the time of the counter overflow interrupt.  Is that right?
> 
> Indeed, whenever a mmap/munmap happens of a PROT_EXEC range we record
> that information so that we can relate the userspace IPs to some file
> and hence the actual userspace code.

Ah, I see, PROT_EXEC identifies the executable code sections in particular.

Thanks :-)

- Corey

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