Re: [PATCH 1/2 v3] mm: vmscan: do not pass reclaimed slab to vmpressure

[Minchan Kim]

On Tue, Jan 31, 2017 at 02:32:08PM +0530, Vinayak Menon wrote:
> During global reclaim, the nr_reclaimed passed to vmpressure
> includes the pages reclaimed from slab. But the corresponding
> scanned slab pages is not passed. This can cause total reclaimed
> pages to be greater than scanned, causing an unsigned underflow
> in vmpressure resulting in a critical event being sent to root
> cgroup. So do not consider reclaimed slab pages for vmpressure
> calculation. The reclaimed pages from slab can be excluded because
> the freeing of a page by slab shrinking depends on each slab's
> object population, making the cost model (i.e. scan:free) different
> from that of LRU. Also, not every shrinker accounts the pages it
> reclaims. This is a regression introduced by commit 6b4f7799c6a5
> ("mm: vmscan: invoke slab shrinkers from shrink_zone()").
> 
> Signed-off-by: Vinayak Menon <vinmenon@xxxxxxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>