Re: [PATCH 0/3] OOM detection rework v4

[Michal Hocko <mhocko@kernel.org>]

On Fri 26-02-16 18:27:16, Hillf Danton wrote:
> >> 
> > > --- a/mm/page_alloc.c	Thu Feb 25 15:43:18 2016
> > > +++ b/mm/page_alloc.c	Fri Feb 26 15:18:55 2016
> > > @@ -3113,6 +3113,8 @@ should_reclaim_retry(gfp_t gfp_mask, uns
> > >  	struct zone *zone;
> > >  	struct zoneref *z;
> > >
> > > +	if (order <= PAGE_ALLOC_COSTLY_ORDER)
> > > +		return true;
> > 
> > This is defeating the whole purpose of the rework - to behave
> > deterministically. You have just disabled the oom killer completely.
> > This is not the way to go
> > 
> Then in another direction, below is what I can do.
> 
> thanks
> Hillf
> --- a/mm/page_alloc.c	Thu Feb 25 15:43:18 2016
> +++ b/mm/page_alloc.c	Fri Feb 26 18:14:59 2016
> @@ -3366,8 +3366,11 @@ retry:
>  		no_progress_loops++;
>  
>  	if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
> -				 did_some_progress > 0, no_progress_loops))
> +				 did_some_progress > 0, no_progress_loops)) {
> +		/* Burn more cycles if any zone seems to satisfy our request */
> +		no_progress_loops /= 2;

No, I do not think this makes any sense. If we need more retry loops
then we can do it by increasing MAX_RECLAIM_RETRIES.

>  		goto retry;
> +	}
>  
>  	/* Reclaim has failed us, start killing things */
>  	page = __alloc_pages_may_oom(gfp_mask, order, ac, &did_some_progress);

-- 
Michal Hocko
SUSE Labs