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

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Message-Id: <ec5cae10-a7d2-a926-bd65-59a2a48a3254@linux.vnet.ibm.com>
Date:   Fri, 2 Sep 2016 22:25:02 +0530
From:   Hari Bathini <hbathini@...ux.vnet.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     ast@...com, lkml <linux-kernel@...r.kernel.org>, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, mingo@...hat.com,
        daniel@...earbox.net, rostedt@...dmis.org,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        ebiederm@...ssion.com, sargun@...gun.me,
        Aravinda Prasad <aravinda@...ux.vnet.ibm.com>,
        brendan.d.gregg@...il.com
Subject: Re: [PATCH v2 1/2] perf: add container identifier entry in perf
 sample data



On Friday 02 September 2016 07:29 PM, Peter Zijlstra wrote:
> 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.

Ok. Thanks!

>
>>> 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?
>

Yes, Peter. /proc/$pid/ns
Will work on this and respin...

Thanks
Hari