From: Ingo Molnar <mingo@elte.hu>
Date: Thu, 11 Dec 2008 07:38:42 +0000 (+0100)
Subject: perf counters: add support for group counters
X-Git-Tag: v2.6.31-rc1~383^2~578
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=04289bb9891882202d7e961c4c04d2376930e9f9;p=pandora-kernel.git

perf counters: add support for group counters

Impact: add group counters

This patch adds the "counter groups" abstraction.

Groups of counters behave much like normal 'single' counters, with a
few semantic and behavioral extensions on top of that.

A counter group is created by creating a new counter with the open()
syscall's group-leader group_fd file descriptor parameter pointing
to another, already existing counter.

Groups of counters are scheduled in and out in one atomic group, and
they are also roundrobin-scheduled atomically.

Counters that are member of a group can also record events with an
(atomic) extended timestamp that extends to all members of the group,
if the record type is set to PERF_RECORD_GROUP.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
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