Re: [PATCH 08/27] mm, vmscan: Make kswapd reclaim in terms of nodes

Johannes Weiner
2016-02-28T16:16:58Z

On Tue, Feb 23, 2016 at 03:04:31PM +0000, Mel Gorman wrote:
> @@ -3299,20 +3191,37 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
> break;
>
> /*
> + * Stop reclaiming if any eligible zone is balanced and clear
> + * node writeback or congested.
> + */
> + for (i = 0; i <= classzone_idx; i++) {
> + zone = pgdat->node_zones + i;
> + if (!populated_zone(zone))
> + continue;
> +
> + if (zone_balanced(zone, sc.order, 0, classzone_idx)) {
> + clear_bit(PGDAT_CONGESTED, &pgdat->flags);
> + clear_bit(PGDAT_DIRTY, &pgdat->flags);
> + goto out;
> + }
> + }
> +
> + /*
> * Raise priority if scanning rate is too low or there was no
> * progress in reclaiming pages
> */
> if (raise_priority || !sc.nr_reclaimed)
> sc.priority--;
> - } while (sc.priority >= 1 &&
> - !pgdat_balanced(pgdat, order, classzone_idx));
> + } while (sc.priority >= 1);
>
> out:
> /*
> - * Return the highest zone idx we were reclaiming at so
> - * prepare_kswapd_sleep() makes the same decisions as here.
> + * Return the order we were reclaiming at so prepare_kswapd_sleep()
> + * makes a decision on the order we were last reclaiming at. However,
> + * if another caller entered the allocator slow path while kswapd
> + * was awake, order will remain at the higher level
> */
> - return end_zone;
> + return order;

It's sc.order that's updated based on fragmentation, not order.

There is also a now-stale comment above the function saying it returns
the highest reclaimed zone index.

Otherwise, the patch looks good to me.

Acked-by: Johannes Weiner <hannes@cmpxchg.org>