Re: [PATCH 04/11] perf: Make perf_cgroup_from_task() global

From: Matt Fleming
Date: Wed Oct 08 2014 - 06:28:09 EST

On Tue, 07 Oct, at 08:51:57PM, Peter Zijlstra wrote:
> On Wed, Sep 24, 2014 at 03:04:08PM +0100, Matt Fleming wrote:
> > From: Matt Fleming <matt.fleming@xxxxxxxxx>
> >
> > Move perf_cgroup_from_task() from kernel/events to include/ along with
> > the necessary struct definitions, so that it can be used by the PMU
> > code.
> >
> > The upcoming Intel Cache Monitoring PMU driver assigns monitoring IDs
> > based on a task's association with a cgroup - all tasks in the same
> > cgroup share an ID. We can use perf_cgroup_from_task() to track this
> > association.
> Not yet having read the rest of the patches and maybe understanding
> things wrong, that doesn't sound right.
> The RMID should be associated with events, not groups. The event can be
> associated with whatever perf provides {task, cgroup, cpu}.

I think I just wrote the commit message in a goofy way.

What we actually use perf_cgroup_from_task() for is to figure out when
to prohibit an event from being created if it overlaps/conflicts with an
existing event.

I'll rewrite the commit message to be clearer.

Matt Fleming, Intel Open Source Technology Center
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