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

Eric W. Biederman
2016-07-12T14:09:20Z

Peter Zijlstra <peterz@infradead.org> writes:

> On Tue, Jul 12, 2016 at 03:41:42PM +0300, Nikolay Borisov wrote:
>
>> Namespaces and cgroups are completely orthogonal to one another.
>
> Then how do you specify what your new 'root' is? Surely you must first
> create a cgroup and then confine yourself to that?
>
>> Also in the v1 of cgroups it's possible to have a process member of
>> more than 1 cgroup.
>
> Yeah, so? We only care about the perf controller obviously.

I completely misread the description of this, or I would have something
earlier. For some reason I thought he was talking about the perf
controller.

As I recall the tricky part of this was to have tracing that was safe
and usable inside of a container. If you can align a per cgroup with
your container that is probably sufficient for the select of processes.

At the same time there is a real desire to have identifiers like pids
translated into the appropriate form for inside of the container.
Without that translation they are meaningless inside a container.
Further it is necessary to be certain the trancing that is used is is
safe for unprivileged users.

I don't think I ever suggested or approved of the concept of a perf
namespace and that sounds a bit dubious to me.

Eric