Re: [PATCH 1/5] mm: Add __GFP_NO_OOM_KILL flag

Andrew Morton
2009-05-07T20:56:15Z

On Thu, 7 May 2009 22:38:13 +0200
"Rafael J. Wysocki" <rjw-KKrjLPT3xs0@public.gmane.org> wrote:

> On Thursday 07 May 2009, David Rientjes wrote:
> > On Thu, 7 May 2009, Rafael J. Wysocki wrote:
> >
> > > OK, let's try with __GFP_NO_OOM_KILL first. If there's too much disagreement,
> > > I'll use the freezer-based approach instead.
> > >
> >
> > Third time I'm going to suggest this, and I'd like a response on why it's
> > not possible instead of being ignored.
> >
> > All of your tasks are in D state other than kthreads, right? That means
> > they won't be in the oom killer (thus no zones are oom locked), so you can
> > easily do this
> >
> > struct zone *z;
> > for_each_populated_zone(z)
> > zone_set_flag(z, ZONE_OOM_LOCKED);
> >
> > and then
> >
> > for_each_populated_zone(z)
> > zone_clear_flag(z, ZONE_OOM_LOCKED);
> >
> > The serialization is done with trylocks so this will never invoke the oom
> > killer because all zones in the allocator's zonelist will be oom locked.
> >
> > Why does this not work for you?
>
> Well, it might work too, but why are you insisting? How's it better than
> __GFP_NO_OOM_KILL, actually?
>
> Andrew, what do you think about this?

I don't think I understand the proposal. Is it to provide a means by
which PM can go in and set a state bit against each and every zone? If
so, that's still a global boolean, only messier.