Re: [PATCH v2 1/2] perf: add container identifier entry in perf sample data

[Peter Zijlstra]

On Fri, Sep 02, 2016 at 07:25:31PM +0530, Hari Bathini wrote:
> >I'm thinking this value is mostly the same for tasks, just like COMM and
> 
> I think so, too. Namespaces aren't changed that often for tasks...
> 
> >MMAP. Could we therefore not emit (sideband) events whenever a task
> >changes namespace and get the same information but with tons less data?
> 
> You mean, something like PERF_RECORD_NAMESPACE that
> emits events on fork, clone, setns..?

Yep.

> 
> >That also gives the possibility of recording all namespaces, not just
> >the one.
> 
> True. If we record all namespaces, container identifier interpretation
> can be left to the userspace to decide, which is much more flexible...

The only complication is initial state, on record start you'd have to
trawl /proc and generate 'fake' namespace records for all (relevant)
tasks.

We do the same with MMAP records, we parse /proc/$pid/maps for that.

Is this namespace stuff available in /proc somewhere?