linux-kernel - Re: [RFC PATCH 2/2] perf: Filter events based on perf-namespace

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Date:	Tue, 12 Jul 2016 13:47:34 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Aravinda Prasad <aravinda@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, rostedt@...dmis.org,
	mingo@...hat.com, paulus@...ba.org, acme@...nel.org,
	ebiederm@...ssion.com, hbathini@...ux.vnet.ibm.com,
	ananth@...ibm.com
Subject: Re: [RFC PATCH 2/2] perf: Filter events based on perf-namespace

On Tue, Jul 12, 2016 at 02:56:17PM +0530, Aravinda Prasad wrote:
> 
> 
> On Monday 27 June 2016 09:20 PM, Peter Zijlstra wrote:
> > On Tue, Jun 14, 2016 at 10:19:51PM +0530, Aravinda Prasad wrote:
> >> Whenever perf tool is executed inside a container, this
> >> patch restricts the events to the perf-namespace in which
> >> the perf tool is executing.
> >>
> >> This patch is based on the existing support available
> >> for tracing with cgroups.
> >>
> >> TODO:
> >>     - Avoid code duplication.
> > 
> > Can't you, at perf_event_open() time, convert a per-cpu event into a
> > per-cpu-per-cgroup event for these namespace thingies?
> > 
> > That seems to immediately and completely remove all that duplication.
> 
> Sorry for the delay in the response.
> 
> I was looking into a way how a per-cpu event can be converted to
> per-cpu-per-cgroup event at perf_event_open() but could not figure out
> how to do this conversion. The cgroup event expects the fd of the cgroup
> directory in cgroupfs and in this case we don't have any fd passed in.
> Not sure if I am missing anything.

Would not the current namespace have a link to the correct cgroup?
Wasn't that the entire point of the namespace thing?