On Wed, 20 Oct 2010 09:11:09 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > On Tue, 19 Oct 2010 14:00:58 -0700 > Greg Thelen <gthelen@xxxxxxxxxx> wrote: > (snip) > > +When use_hierarchy=0, each cgroup has independent dirty memory usage and limits. > > + > > +When use_hierarchy=1, a parent cgroup increasing its dirty memory usage will > > +compare its total_dirty memory (which includes sum of all child cgroup dirty > > +memory) to its dirty limits. This keeps a parent from explicitly exceeding its > > +dirty limits. However, a child cgroup can increase its dirty usage without > > +considering the parent's dirty limits. Thus the parent's total_dirty can exceed > > +the parent's dirty limits as a child dirties pages. > > Hmm. in short, dirty_ratio in use_hierarchy=1 doesn't work as an user expects. > Is this a spec. or a current implementation ? > > I think as following. > - add a limitation as "At setting chidlren's dirty_ratio, it must be below parent's. > If it exceeds parent's dirty_ratio, EINVAL is returned." > > Could you modify setting memory.dirty_ratio code ? > Then, parent's dirty_ratio will never exceeds its own. (If I understand correctly.) > > "memory.dirty_limit_in_bytes" will be a bit more complecated, but I think you can. > I agree. At the first impression, this limitation seems a bit overkill for me, because we allow memory.limit_in_bytes of a child bigger than that of parent now. But considering more, the situation is different, because usage_in_bytes never exceeds limit_in_bytes. Thanks, Daisuke Nishimura. -- 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>