On Wed, Mar 20, 2013 at 05:18:47PM +0100, Michal Hocko wrote:
> On Sun 17-03-13 13:04:07, Mel Gorman wrote:
> [...]
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 88c5fed..4835a7a 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -2593,6 +2593,32 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
> > }
> >
> > /*
> > + * kswapd shrinks the zone by the number of pages required to reach
> > + * the high watermark.
> > + */
> > +static void kswapd_shrink_zone(struct zone *zone,
> > + struct scan_control *sc,
> > + unsigned long lru_pages)
> > +{
> > + unsigned long nr_slab;
> > + struct reclaim_state *reclaim_state = current->reclaim_state;
> > + struct shrink_control shrink = {
> > + .gfp_mask = sc->gfp_mask,
> > + };
> > +
> > + /* Reclaim above the high watermark. */
> > + sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone));
>
> OK, so the cap is at high watermark which sounds OK to me, although I
> would expect balance_gap being considered here. Is it not used
> intentionally or you just wanted to have a reasonable upper bound?
>
It's intentional. The balance_gap is taken into account before the
decision to shrink but not afterwards. As the watermark check after
shrinking is based on just the high watermark, I decided to have
shrink_zone reclaim on that basis.
--
Mel Gorman
SUSE Labs
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