Re: [RFC 1/3] mm, oom: refactor oom detection

[Michal Hocko <mhocko@suse.cz>]

On Fri 20-11-15 15:27:39, David Rientjes wrote:
> On Fri, 20 Nov 2015, Michal Hocko wrote:
> 
> > > > +		unsigned long reclaimable;
> > > > +		unsigned long target;
> > > > +
> > > > +		reclaimable = zone_reclaimable_pages(zone) +
> > > > +			      zone_page_state(zone, NR_ISOLATED_FILE) +
> > > > +			      zone_page_state(zone, NR_ISOLATED_ANON);
> > > 
> > > Does NR_ISOLATED_ANON mean anything relevant here in swapless 
> > > environments?
> > 
> > It should be 0 so I didn't bother to check for swapless configuration.
> > 
> 
> I'm not sure I understand your point, memory compaction certainly 
> increments NR_ISOLATED_ANON and that would be considered unreclaimable in 
> a swapless environment, correct?

My bad. I have completely missed that compaction/migration is updating
the counter as well. I would expect that the number shouldn't too large
to matter but I guess it will be better to simply exclude it. I will
fold this to the first patch.

Thanks
---
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 54476e71b572..7d885d7fae86 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3197,8 +3197,10 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
 		unsigned long target;
 
 		reclaimable = zone_reclaimable_pages(zone) +
-			      zone_page_state(zone, NR_ISOLATED_FILE) +
-			      zone_page_state(zone, NR_ISOLATED_ANON);
+			      zone_page_state(zone, NR_ISOLATED_FILE);
+		if (get_nr_swap_pages() > 0)
+			reclaimable += zone_page_state(zone, NR_ISOLATED_ANON);
+
 		target = reclaimable;
 		target -= DIV_ROUND_UP(stall_backoff * target, MAX_STALL_BACKOFF);
 		target += free;

-- 
Michal Hocko
SUSE Labs

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