linux-kernel - perf_counter: resetting a event counter

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Date:	Mon, 04 May 2009 15:15:11 -0700
From:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>
Subject: perf_counter: resetting a event counter

Hi,

In implementing the PAPI_reset function, whose purpose is to reset all 
of the counters in an event set, I found that [it appears] there is no 
straight-forward way to implement this function using "Performance 
Couunters for Linux".  My current implementation just closes the 
counters and reopens them again.  This is not a elegant solution, nor is 
the other alternative that occurred to me: maintain a "virtual" counter 
in user space, maintained using a base count, which is subtracted off of 
the current perf_counter value of a particular counter.

Is there a way that I missed to reset an event counter?  If not, I'd 
like to request that a new ioctl command be added to support this ability.

Thanks for your consideration,

- Corey

Corey Ashford
Software Engineer
IBM Linux Technology Center, Linux Toolchain
Beaverton, OR
503-578-3507
cjashfor@...ibm.com

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