On Wed, Jul 28, 2010 at 11:35:29AM +0900, KAMEZAWA Hiroyuki wrote: > On Tue, 27 Jul 2010 22:30:27 -0400 > Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > > > > Index: mmotm-2.6.35-0719/Documentation/cgroups/cgroups.txt > > > =================================================================== > > > --- mmotm-2.6.35-0719.orig/Documentation/cgroups/cgroups.txt > > > +++ mmotm-2.6.35-0719/Documentation/cgroups/cgroups.txt > > > @@ -621,6 +621,15 @@ and root cgroup. Currently this will onl > > > the default hierarchy (which never has sub-cgroups) and a hierarchy > > > that is being created/destroyed (and hence has no sub-cgroups). > > > > > > +void custom_id(struct cgroup_subsys *ss, struct cgroup *cgrp) > > > + > > > +Called at assigning a new ID to cgroup subsystem state struct. This > > > +is called when ss->use_id == true. If this function is not provided, > > > +a new ID is automatically assigned. If you enable ss->use_id, > > > +you can use css_lookup() and css_get_next() to access "css" objects > > > +via IDs. > > > + > > > > Couple of lines to explain why a subsystem would like to assign its > > own ids and not be happy with generic cgroup assigned id be helpful. > > In this case, I think you are using this id as index into array > > and want to control the index, hence you seem to be doing it. > > > > But I am not sure again why do you want to control index? > > > > Now, the subsystem allocation/id-allocation order is > > ->create() > alloc_id. > > Otherwise "id" of memory cgroup is just determined by the place in virtual-indexed > array. > As > memcg = mem_cgroup_base + id > > This "id" is determined at create(). > > If "id" is determined regardless of memory cgroup's placement, it's of no use. > My original design of css_id() allocates id in create() but it was moved to > generic part. So, this is expected change in my plan. > > We have 2 choices. > id = alloc_id() > create(id) > or > this patch. > > Both are okay for me. But alloc id before create() may add some ugly rollback. Ok, so in current design at the time of mem_cgroup instantiation css_id is not available so you don't know at what index to put the newly instantiated mem_cgroup object, hence the notion of let subsys decide the css_id and cgroup can query from subsystem later. I don't have any preference. Anything simple works.. Vivek -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>