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Re: [PATCH v4 0/3] perf: add support for analyzing events for containers

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On Fri, Dec 16, 2016 at 12:06:55AM +0530, Hari Bathini wrote:
> This patch-set overcomes this limitation by using cgroup identifier as
> container unique identifier. A new PERF_RECORD_NAMESPACES event that
> records namespaces related info is introduced, from which the cgroup
> namespace's device & inode numbers are used as cgroup identifier. This
> is based on the assumption that each container is created with it's own
> cgroup namespace allowing assessment/analysis of multiple containers
> using cgroup identifier.

Why choose cgroups when the kernel dispenses namespace-unique
identifiers. Cgroup membership can be arbitrary.  Moreover, cgroup and
namespace destruction are handled by separate subsystems.  It's possible
to have a cgroup notifier run prior to network namespace teardown
occurring.

If it were me, I'd re-use existing convention to identify the namespaces
you want to monitor.  The code in nsenter(1) can take a namespace that's
been bind mount'd on a file, or extract the ns information from a task
in /procfs.

My biggest concern is how the sample data is handled after it has been
collected.  Both namespaces and cgroups don't survive reboots.  Will the
records will contain all the persistent state needed to run a report or
script command at a later date?

Does this code attempt to enter alternate namespaces in order to record
stack/symbol information for a '-g' style trace?  If so, how are you
holding on to that information?  There's no guarantee that a particular
container will be alive or have its filesystems reachable from the host
if the trace data is evaluated at a later time.

-K

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[PATCH v4 0/3] perf: add support for analyzing events for containers Hari Bathini <hbathini@linux.vnet.ibm.com> - 2016-12-15 19:40 +0100
  [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include  namespaces related info Hari Bathini <hbathini@linux.vnet.ibm.com> - 2016-12-15 19:40 +0100
    Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include  namespaces related info Peter Zijlstra <peterz@infradead.org> - 2016-12-15 19:50 +0100
      Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include  namespaces related info Hari Bathini <hbathini@linux.vnet.ibm.com> - 2016-12-16 08:10 +0100
        Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include  namespaces related info Peter Zijlstra <peterz@infradead.org> - 2016-12-16 09:30 +0100
          Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include  namespaces related info Hari Bathini <hbathini@linux.vnet.ibm.com> - 2016-12-16 19:30 +0100
            Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include  namespaces related info Peter Zijlstra <peterz@infradead.org> - 2016-12-16 21:10 +0100
              Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include  namespaces related info Hari Bathini <hbathini@linux.vnet.ibm.com> - 2016-12-21 14:10 +0100
                Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include  namespaces related info Peter Zijlstra <peterz@infradead.org> - 2016-12-21 14:30 +0100
                Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include  namespaces related info Hari Bathini <hbathini@linux.vnet.ibm.com> - 2016-12-21 17:00 +0100
                Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include namespaces related info ebiederm@xmission.com (Eric W. Biederman) - 2016-12-22 08:30 +0100
                Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include  namespaces related info Peter Zijlstra <peterz@infradead.org> - 2016-12-22 09:00 +0100
                Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include namespaces related info ebiederm@xmission.com (Eric W. Biederman) - 2016-12-22 11:30 +0100
                Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include  namespaces related info Peter Zijlstra <peterz@infradead.org> - 2016-12-22 14:30 +0100
                Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include namespaces related info ebiederm@xmission.com (Eric W. Biederman) - 2016-12-22 19:30 +0100
  [PATCH v4 2/3] perf tool: add PERF_RECORD_NAMESPACES to include  namespaces related info Hari Bathini <hbathini@linux.vnet.ibm.com> - 2016-12-15 19:40 +0100
    Re: [PATCH v4 2/3] perf tool: add PERF_RECORD_NAMESPACES to include  namespaces related info Jiri Olsa <jolsa@redhat.com> - 2016-12-17 18:50 +0100
      Re: [PATCH v4 2/3] perf tool: add PERF_RECORD_NAMESPACES to include  namespaces related info Hari Bathini <hbathini@linux.vnet.ibm.com> - 2016-12-21 14:20 +0100
  Re: [PATCH v4 0/3] perf: add support for analyzing events for  containers Krister Johansen <kjlx@templeofstupid.com> - 2016-12-29 02:50 +0100
    Re: [PATCH v4 0/3] perf: add support for analyzing events for  containers Hari Bathini <hbathini@linux.vnet.ibm.com> - 2017-01-03 12:30 +0100

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