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Subject: perf and cgroup event scheduling
From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Eranian <eranian@google.com>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel <linux-kernel@vger.kernel.org>,
        Oleg Nesterov <oleg@redhat.com>
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Date: Thu, 31 Mar 2011 15:27:07 +0200
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Hi Stephane,

while trying to make sense of various other fun event scheduling issues,
I noticed that perf_cgroup_switch() isn't always doing the right thing.

So we typically want to schedule: CPU-pinned, TASK-pinned, CPU-flexible
TASK-flexible, however the current code doesn't respect that.

In particular perf_cgroup_sched_in() is placed wrong, it should be
_before_ we schedule in the task contexts.

There's further complications with things like perf_install_in_context()
and perf_cgroup_move(), but those are either rare or 'interesting' to
fix.