linux-kernel - perf: PERF_EVENT_IOC_PERIOD on ARM vs everywhere else

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Message-ID: <alpine.DEB.2.10.1310272233120.12721@vincent-weaver-1.um.maine.edu>
Date:	Sun, 27 Oct 2013 22:37:46 -0400 (EDT)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	linux-kernel@...r.kernel.org
cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Will Deacon <will.deacon@....com>
Subject: perf: PERF_EVENT_IOC_PERIOD on ARM vs everywhere else

Hello

it was pointed out to me that in the 3.7 kernel (more specifically,
3581fe0ef37ce12ac7a4f74831168352ae848edc ) a change was made in the
ARM architecture to change how PERF_EVENT_IOC_PERIOD is handled.

Unlike other architectures, post-3.7 ARM updates the period right away 
rather than waiting until the next overflow.

I can't find any discussion as to why this change was made.

Should other architectures be updated to?  I just wanted to find out the 
rationale for this before I update the manpage to reflect the difference 
in behaviors between architectures.

Vince
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