Re: [PATCH v2] /proc/pid/status: show all sets of pid according to ns

[Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>]

On 05/29/2014 09:59 AM, Vasily Kulikov wrote:
> On Wed, May 28, 2014 at 23:27 +0400, Pavel Emelyanov wrote:
>> On 05/28/2014 10:28 PM, Vasily Kulikov wrote:
>>> On Wed, May 28, 2014 at 16:44 +0400, Pavel Emelyanov wrote:
>>> It will be simplier
>>> to parse the file -- if 'ns_ids' file contains some ID then this ID for
>>> every ns can be obtained regardless of the specific ID name (SID, PID,
>>> PGID, etc.).
>>
>> True, but given a task PID how to determine which pid namespaces it lives in
>> to get the idea of how PIDs map to each other? Maybe we need some explicit
>> API for converting (ID, NS1, NS2) into (ID)?
> 
> AFAIU the idea of the patch is to add a new debugging information which
> can be trivially obtained via 'cat /proc/...':

I agree, but this ability will be very useful by checkpoint-restore project
too and I'd really appreciate if the API we have for that would be scalable
enough. Per-task proc file works for me, but how about sid-s and pgid-s?

> ] We need a direct method of getting the pid inside containers.
> ] If some issues occurred inside container guest, host user
> ] could not know which process is in trouble just by guest pid:
> ] the users of container guest only knew the pid inside containers.
> ] This will bring obstacle for trouble shooting.
> 
> A new syscall might complicate trouble shooting by admin.

Pure syscall -- yes. What if we teach the ps and top utilities to show additional
info? I think that would help.

Thanks,
Pavel