Messages in this thread | | | Date | Wed, 30 Nov 2011 10:05:37 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [rfc 2/3] fs, proc: Introduce the Children: line in /proc/<pid>/status |
| |
On Wed, Nov 30, 2011 at 02:00:09PM +0900, KAMEZAWA Hiroyuki wrote: > On Tue, 29 Nov 2011 23:12:54 +0400 > Cyrill Gorcunov <gorcunov@openvz.org> wrote: > > > From: Pavel Emelyanov <xemul@parallels.com> > > > > There is no easy way to make a reverse parent->children chain > > from the task status, in turn children->parent provided with "PPid" > > field. > > > > So instead of walking over all pids in system to figure out what > > children the task have -- we add explicit "Children" member to > > /proc/<pid>/status since kernel already knows this kind of information > > but it was not yet exported. > > > > Signed-off-by: Pavel Emelyanov <xemul@parallels.com> > > Acked-by: Serge Hallyn <serge.hallyn@canonical.com> > > Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> > > I may be too pessimistic but what amount of overhead will this add to > ps -elf/ top ? Assuming an environment 'ps -elf' is called once per a sec, > if there are 2000 processes, task_list lock is taken 2000 times by this patch. >
Hi Kame, good point! Yes, it introduces latency on high loaded systems. I must admit I tested this patch on a regular system, where not that much processes were launched but technically I think more correct would be to switch to children file. I'll tune up the patch. Thanks!
> Isn't it better to add /proc/<pid>/children file or dir (as task)? > > Thanks, > -Kame >
| |