Re: [PATCH] mm/page_alloc: Wait for oom_lock before retrying.

[Michal Hocko <mhocko@suse.com>]

On Mon 12-12-16 12:49:03, Petr Mladek wrote:
> On Mon 2016-12-12 10:07:03, Michal Hocko wrote:
> > On Sat 10-12-16 20:24:57, Tetsuo Handa wrote:
[...]
> > > The introduction of uncontrolled
> > > 
> > >   warn_alloc(gfp_mask, "page allocation stalls for %ums, order:%u", ...);
> 
> I am just curious that there would be so many messages.
> If I get it correctly, this warning is printed
> once every 10 second. Or am I wrong?

Yes it is once per 10s per allocation context. Tetsuo's test case is
generating hundreds of such allocation paths which are hitting the
warn_alloc path. So they can meet there and generate a lot of output.
Now we have __ratelimit here which should help but most probably needs
some better tunning.

I am also considering to use a per warn_alloc lock which would also help
to make the output nicer (not interleaving for parallel callers).

> Well, you might want to consider using
> 
> 		stall_timeout *= 2;
> 
> instead of adding the constant 10 * HZ.

This wouldn't help in the above situation.
-- 
Michal Hocko
SUSE Labs

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