Messages in this thread |  | | Date | Fri, 17 Jul 2015 17:50:52 +0530 | | From | Aravinda Prasad <> | | Subject | Re: [RFC PATCH] perf: Container-aware tracing support |
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On Friday 17 July 2015 03:49 PM, Peter Zijlstra wrote: > On Wed, Jul 15, 2015 at 09:51:52PM +0530, Aravinda Prasad wrote: >>>> + } else if (task_active_pid_ns(current) != &init_pid_ns) { >>> >>> Why the pid namespace? >> >> This comes from my understanding of container -- having at least a >> separate PID namespace with processes inside a container grouped into a >> single perf_event cgroups subsystem. >> >> I know there are other ways to define a container, however, I thought I >> start with the above one. > > Right, but you should at least mention this, preferably in a comment.
Yes. I should have done that.
> >>> >>>> + /* Don't set event->cgrp if task belongs to root cgroup */ >>>> + if (task_css_is_root(current, perf_event_cgrp_id)) >>>> + return ret; >>> >>> So if you have the root perf_cgroup inside your container you can >>> escape? >> >> If we have root perf_cgroup inside the container then even if we set >> event->cgrp we will be including all processes in the system. > > Yes, that's what I said. Why does that make sense?
We assume that processes are grouped into a single perf_event subsystem. If we have root perf_cgroup, from our assumption, implies we are not invoked from a container context. However, not sure if this assumption is right.
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-- Regards, Aravinda
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