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

[Peter Zijlstra]

On Tue, Aug 30, 2016 at 09:57:02PM +0530, Hari Bathini wrote:
> Currently, there is no mechanism to filter events based on containers.
> perf -G can be used, but it will not filter events for the containers
> created after perf is invoked, making it difficult to assess/analyze
> performance issues of multiple containers at once. This limitation can
> be overcome, if there is a standard kernel identifier for containers.
> 
> This patch introduces a container identifier entry field in perf sample
> data to identify or distinguish sample data of different containers. It
> uses the cgroup namespace inode number of a given task as it's container
> identifier (cid). Alternatively, inode number of pid namespace can also
> be used as cid. This patch assumes each container is created with it's
> own cgroup namespace.

I'm thinking this value is mostly the same for tasks, just like COMM and
MMAP. Could we therefore not emit (sideband) events whenever a task
changes namespace and get the same information but with tons less data?

That also gives the possibility of recording all namespaces, not just
the one.