On Mon, 7 Feb 2011 18:13:22 -0800 (PST)
David Rientjes <rientjes@xxxxxxxxxx> wrote:
> On Tue, 8 Feb 2011, KAMEZAWA Hiroyuki wrote:
>
> > > +static int mem_cgroup_oom_delay_millisecs_write(struct cgroup *cgrp,
> > > + struct cftype *cft, u64 val)
> > > +{
> > > + struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
> > > + struct mem_cgroup *iter;
> > > +
> > > + if (val > MAX_SCHEDULE_TIMEOUT)
> > > + return -EINVAL;
> > > +
> > > + for_each_mem_cgroup_tree(iter, memcg) {
> > > + iter->oom_delay = msecs_to_jiffies(val);
> > > + memcg_oom_recover(iter);
> > > + }
> > > + return 0;
> >
> > Seems nicer and it seems you tries to update all children cgroups.
> >
> > BTW, with above code, with following heirarchy,
> >
> > A
> > /
> > B
> > /
> > C
> >
> > When a user set oom_delay in order as A->B->C, A,B,C can have 'different' numbers.
> > When a user set oom_delay in order as C->B->A, A,B,C will have the same numbers.
> >
> > This intreface seems magical, or broken.
> >
>
> It's not really magical, it just means that if you change the delay for a
> memcg that you do so for all of its children implicitly as well.
>
But you didn't explain the bahavior in Documenation.
> An alternative would be to ensure that a child memcg may never have a
> delay greater than the delay of its parent. Would you prefer that
> instead?
>
I don't think such limitation makes sense.
My point is just that the behavior is very special in current memcg interfaces.
They do
- It's not allowed to set attribute to no-children, no-parent cgroup
So, please explain above behavior in Documenation.
Thanks,
-Kame
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