Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of RAM that should be free

[Marc MERLIN]

On Mon, Nov 28, 2016 at 08:23:15AM +0100, Michal Hocko wrote:
> Marc, could you try this patch please? I think it should be pretty clear
> it should help you but running it through your use case would be more
> than welcome before I ask Greg to take this to the 4.8 stable tree.
> 
> Thanks!
> 
> On Wed 23-11-16 07:34:10, Michal Hocko wrote:
> [...]
> > commit b2ccdcb731b666aa28f86483656c39c5e53828c7
> > Author: Michal Hocko <mhocko@xxxxxxxx>
> > Date:   Wed Nov 23 07:26:30 2016 +0100
> > 
> >     mm, oom: stop pre-mature high-order OOM killer invocations
> >     
> >     31e49bfda184 ("mm, oom: protect !costly allocations some more for
> >     !CONFIG_COMPACTION") was an attempt to reduce chances of pre-mature OOM
> >     killer invocation for high order requests. It seemed to work for most
> >     users just fine but it is far from bullet proof and obviously not
> >     sufficient for Marc who has reported pre-mature OOM killer invocations
> >     with 4.8 based kernels. 4.9 will all the compaction improvements seems
> >     to be behaving much better but that would be too intrusive to backport
> >     to 4.8 stable kernels. Instead this patch simply never declares OOM for
> >     !costly high order requests. We rely on order-0 requests to do that in
> >     case we are really out of memory. Order-0 requests are much more common
> >     and so a risk of a livelock without any way forward is highly unlikely.
> >     
> >     Reported-by: Marc MERLIN <marc@xxxxxxxxxxx>
> >     Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

Tested-by: Marc MERLIN <marc@xxxxxxxxxxx>

Marc

> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index a2214c64ed3c..7401e996009a 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -3161,6 +3161,16 @@ should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_fla
> >  	if (!order || order > PAGE_ALLOC_COSTLY_ORDER)
> >  		return false;
> >  
> > +#ifdef CONFIG_COMPACTION
> > +	/*
> > +	 * This is a gross workaround to compensate a lack of reliable compaction
> > +	 * operation. We cannot simply go OOM with the current state of the compaction
> > +	 * code because this can lead to pre mature OOM declaration.
> > +	 */
> > +	if (order <= PAGE_ALLOC_COSTLY_ORDER)
> > +		return true;
> > +#endif
> > +
> >  	/*
> >  	 * There are setups with compaction disabled which would prefer to loop
> >  	 * inside the allocator rather than hit the oom killer prematurely.
> > -- 
> > Michal Hocko
> > SUSE Labs
> 
> -- 
> Michal Hocko
> SUSE Labs
> 

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