On Wed, 17 Feb 2010 19:45:26 +1100
Nick Piggin <npiggin@xxxxxxx> wrote:
> On Wed, Feb 17, 2010 at 03:04:45PM +0900, KAMEZAWA Hiroyuki wrote:
> > tested on mmotm-Feb11.
> >
> > Balbir-san, Nishimura-san, I want review from both of you.
> >
> > ==
> >
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> >
> > Now, if panic_on_oom=2, the whole system panics even if the oom happend
> > in some special situation (as cpuset, mempolicy....).
> > Then, panic_on_oom=2 means painc_on_oom_always.
> >
> > Now, memcg doesn't check panic_on_oom flag. This patch adds a check.
> >
> > Maybe someone doubts how it's useful. kdump+panic_on_oom=2 is the
> > last tool to investigate what happens in oom-ed system. If a task is killed,
> > the sysytem recovers and used memory were freed, there will be few hint
> > to know what happnes. In mission critical system, oom should never happen.
> > Then, investigation after OOM is very important.
> > Then, panic_on_oom=2+kdump is useful to avoid next OOM by knowing
> > precise information via snapshot.
>
> No I don't doubt it is useful, and I think this probably is the simplest
> and most useful semantic. So thanks for doing this.
>
Thank you for review.
> I hate to pick nits in a trivial patch but I will anyway:
>
>
> > TODO:
> > - For memcg, it's for isolate system's memory usage, oom-notiifer and
> > freeze_at_oom (or rest_at_oom) should be implemented. Then, management
> > daemon can do similar jobs (as kdump) in safer way or taking snapshot
> > per cgroup.
> >
> > CC: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
> > CC: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
> > CC: David Rientjes <rientjes@xxxxxxxxxx>
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> > ---
> > Documentation/cgroups/memory.txt | 2 ++
> > Documentation/sysctl/vm.txt | 5 ++++-
> > mm/oom_kill.c | 2 ++
> > 3 files changed, 8 insertions(+), 1 deletion(-)
> >
> > Index: mmotm-2.6.33-Feb11/Documentation/cgroups/memory.txt
> > ===================================================================
> > --- mmotm-2.6.33-Feb11.orig/Documentation/cgroups/memory.txt
> > +++ mmotm-2.6.33-Feb11/Documentation/cgroups/memory.txt
> > @@ -182,6 +182,8 @@ list.
> > NOTE: Reclaim does not work for the root cgroup, since we cannot set any
> > limits on the root cgroup.
> >
> > +Note2: When panic_on_oom is set to "2", the whole system will panic.
> > +
>
> Maybe:
>
> NOTE2: When panic_on_oom is set to "2", the whole system will panic in
> case of an oom event in any cgroup.
>
ok.
> > 2. Locking
> >
> > The memory controller uses the following hierarchy
> > Index: mmotm-2.6.33-Feb11/Documentation/sysctl/vm.txt
> > ===================================================================
> > --- mmotm-2.6.33-Feb11.orig/Documentation/sysctl/vm.txt
> > +++ mmotm-2.6.33-Feb11/Documentation/sysctl/vm.txt
> > @@ -573,11 +573,14 @@ Because other nodes' memory may be free.
> > may be not fatal yet.
> >
> > If this is set to 2, the kernel panics compulsorily even on the
> > -above-mentioned.
> > +above-mentioned. Even oom happens under memoyr cgroup, the whole
> > +system panics.
> memory
>
> >
> > The default value is 0.
> > 1 and 2 are for failover of clustering. Please select either
> > according to your policy of failover.
> > +2 seems too strong but panic_on_oom=2+kdump gives you very strong
> > +tool to investigate a system which should never cause OOM.
>
> I don't think you need say 2 seems too strong because as you rightfully
> say, it has real uses. The hint about using it to investigate OOM
> conditions is good though.
>
ok. I'll update this patch.
Thanks,
-Kame
> >
> > =============================================================
> >
> > Index: mmotm-2.6.33-Feb11/mm/oom_kill.c
> > ===================================================================
> > --- mmotm-2.6.33-Feb11.orig/mm/oom_kill.c
> > +++ mmotm-2.6.33-Feb11/mm/oom_kill.c
> > @@ -471,6 +471,8 @@ void mem_cgroup_out_of_memory(struct mem
> > unsigned long points = 0;
> > struct task_struct *p;
> >
> > + if (sysctl_panic_on_oom == 2)
> > + panic("out of memory(memcg). panic_on_oom is selected.\n");
> > read_lock(&tasklist_lock);
> > retry:
> > p = select_bad_process(&points, mem);
>
--
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>