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SubjectRe: [RFC][PATCH 1/3] memcg: wake up filter in oom waitqueue
On Fri, 12 Mar 2010 11:30:28 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> On Thu, 11 Mar 2010 16:55:59 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > + /* check hierarchy */
> > + if (!css_is_ancestor(&oom_wait_info->mem->css, &wake_mem->css) &&
> > + !css_is_ancestor(&wake_mem->css, &oom_wait_info->mem->css))
> > + return 0;
> > +
> I think these conditions are wrong.
> This can wake up tasks in oom_wait_info->mem when:
>
> 00/ <- wake_mem: use_hierarchy == false
> aa/ <- oom_wait_info->mem: use_hierarchy == true;
>
Hmm. I think this line bails out above case.

> + if (!oom_wait_info->mem->use_hierarchy || !wake_mem->use_hierarchy)
> + return 0;

No ?

Thanks,
-Kame

> It should be:
>
> if((oom_wait_info->mem->use_hierarchy &&
> css_is_ancestor(&wake_mem->css, &oom_wait_info->mem->css)) ||
> (wake_mem->use_hierarchy &&
> css_is_ancestor(&oom_wait_info->mem->css, &wake_mem->css)))
> goto wakeup;
>
> return 0;
>
> But I like the goal of this patch.
>
> Thanks,
> Daisuke Nishimura.
>
> > +wakeup:
> > + return autoremove_wake_function(wait, mode, sync, arg);
> > +}
> > +
> > +static void memcg_wakeup_oom(struct mem_cgroup *mem)
> > +{
> > + /* for filtering, pass "mem" as argument. */
> > + __wake_up(&memcg_oom_waitq, TASK_NORMAL, 0, mem);
> > +}
> > +
> > /*
> > * try to call OOM killer. returns false if we should exit memory-reclaim loop.
> > */
> > bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
> > {
> > - DEFINE_WAIT(wait);
> > + struct oom_wait_info owait;
> > bool locked;
> >
> > + owait.mem = mem;
> > + owait.wait.flags = 0;
> > + owait.wait.func = memcg_oom_wake_function;
> > + owait.wait.private = current;
> > + INIT_LIST_HEAD(&owait.wait.task_list);
> > +
> > /* At first, try to OOM lock hierarchy under mem.*/
> > mutex_lock(&memcg_oom_mutex);
> > locked = mem_cgroup_oom_lock(mem);
> > @@ -1310,31 +1350,18 @@ bool mem_cgroup_handle_oom(struct mem_cg
> > * under OOM is always welcomed, use TASK_KILLABLE here.
> > */
> > if (!locked)
> > - prepare_to_wait(&memcg_oom_waitq, &wait, TASK_KILLABLE);
> > + prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
> > mutex_unlock(&memcg_oom_mutex);
> >
> > if (locked)
> > mem_cgroup_out_of_memory(mem, mask);
> > else {
> > schedule();
> > - finish_wait(&memcg_oom_waitq, &wait);
> > + finish_wait(&memcg_oom_waitq, &owait.wait);
> > }
> > mutex_lock(&memcg_oom_mutex);
> > mem_cgroup_oom_unlock(mem);
> > - /*
> > - * Here, we use global waitq .....more fine grained waitq ?
> > - * Assume following hierarchy.
> > - * A/
> > - * 01
> > - * 02
> > - * assume OOM happens both in A and 01 at the same time. Tthey are
> > - * mutually exclusive by lock. (kill in 01 helps A.)
> > - * When we use per memcg waitq, we have to wake up waiters on A and 02
> > - * in addtion to waiters on 01. We use global waitq for avoiding mess.
> > - * It will not be a big problem.
> > - * (And a task may be moved to other groups while it's waiting for OOM.)
> > - */
> > - wake_up_all(&memcg_oom_waitq);
> > + memcg_wakeup_oom(mem);
> > mutex_unlock(&memcg_oom_mutex);
> >
> > if (test_thread_flag(TIF_MEMDIE) || fatal_signal_pending(current))
> >
>



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