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

[chenhanxiao at cn.fujitsu.com]

> -----Original Message-----
> From: containers-bounces at lists.linux-foundation.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?
> 

Yes, a new syscall is very useful, but it should be another task.
Just for Pids, I think proc file is good enough.

> > ] 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,
- Chen