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

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Date:	Tue, 12 Jul 2016 15:41:42 +0300
From:	Nikolay Borisov <kernel@...p.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	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 07/12/2016 02:47 PM, Peter Zijlstra wrote:
> 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?

Namespaces and cgroups are completely orthogonal to one another. Also in
the v1 of cgroups it's possible to have a process member of more than 1
cgroup.

>