Re: [RFC][PATCH 1/6] memcg: fix pre_destory handler

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Wed, 10 Dec 2008 11:00:35 -0800
Paul Menage <menage@google.com> wrote:

> On Wed, Dec 10, 2008 at 10:35 AM, Paul Menage <menage@google.com> wrote:
> > On Wed, Dec 10, 2008 at 3:29 AM, KAMEZAWA Hiroyuki
> > <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> >>
> >> (BTW, I don't like hierarchy-walk-by-small-locks approarch now because
> >>  I'd like to implement scan-and-stop-continue routine.
> >>  See how readdir() aginst /proc scans PID. It's very roboust against
> >>  very temporal PIDs.)
> >
> > So you mean that you want to be able to sleep, and then contine
> > approximately where you left off, without keeping any kind of
> > reference count on the last cgroup that you touched? OK, so in that
> > case I agree that you would need some kind of hierarch
> 
> Oops, didn't finish that sentence.
> 
> I agree that you'd need some kind of hierarchical-restart. But I'd
> like to play with / look at your cgroup-id patch more closely and see
> if we can come up with something simpler that still does what you
> want.
> 
Sure, I have to do, too. It's still too young.

> One particular problem with the patch as it stands is that the ids
> should be per-css, not per-cgroup, since a css can move between
> hierarchies and hence between cgroups. (Currently only at bind/unbind
> time, but it still results in a cgroup change).
> 

If per-css, looking up function will be
==
struct cgroup_subsys_state *cgroup_css_lookup(subsys_id, id)
==
Do you mean this ? 

ok, I'll implement and see what happens. Maybe I'll move hooks to prepare/destroy IDs
to subsys layer and assign ID only when subsys want IDs.

-Kame




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