On Wed, Apr 10, 2013 at 02:21:42PM +0900, Joonsoo Kim wrote:
> > > > @@ -2673,9 +2674,15 @@ static bool kswapd_shrink_zone(struct zone *zone,
> > > > sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX,
> > > > high_wmark_pages(zone));
> > > > shrink_zone(zone, sc);
> > > >
> > > > - reclaim_state->reclaimed_slab = 0;
> > > > - nr_slab = shrink_slab(&shrink, sc->nr_scanned, lru_pages);
> > > > - sc->nr_reclaimed += reclaim_state->reclaimed_slab;
> > > > + /*
> > > > + * Slabs are shrunk for each zone once per priority or if the
> > > > zone
> > > > + * being balanced is otherwise unreclaimable
> > > > + */
> > > > + if (shrinking_slab || !zone_reclaimable(zone)) {
> > > > + reclaim_state->reclaimed_slab = 0;
> > > > + nr_slab = shrink_slab(&shrink, sc->nr_scanned,
> > > > lru_pages);
> > > > + sc->nr_reclaimed += reclaim_state->reclaimed_slab;
> > > > + }
> > > >
> > > > if (nr_slab == 0 && !zone_reclaimable(zone))
> > > > zone->all_unreclaimable = 1;
> > >
> > > Why shrink_slab() is called here?
> >
> > Preserves existing behaviour.
>
> Yes, but, with this patch, existing behaviour is changed, that is, we call
> shrink_slab() once per priority. For now, there is no reason this function
> is called here. How about separating it and executing it outside of
> zone loop?
>
We are calling it fewer times but it's still receiving the same information
from sc->nr_scanned it received before. With the change you are suggesting
it would be necessary to accumulating sc->nr_scanned for each zone shrunk
and then pass the sum to shrink_slab() once per priority. While this is not
necessarily wrong, there is little or no motivation to alter the shrinkers
in this manner in this series.
--
Mel Gorman
SUSE Labs
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