On Sun 17-03-13 13:04:14, Mel Gorman wrote:
> If kswaps fails to make progress but continues to shrink slab then it'll
> either discard all of slab or consume CPU uselessly scanning shrinkers.
> This patch causes kswapd to only call the shrinkers once per priority.
>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
OK, looks good.
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
> ---
> mm/vmscan.c | 28 +++++++++++++++++++++-------
> 1 file changed, 21 insertions(+), 7 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 7d5a932..84375b2 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2661,9 +2661,10 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
> */
> static bool kswapd_shrink_zone(struct zone *zone,
> struct scan_control *sc,
> - unsigned long lru_pages)
> + unsigned long lru_pages,
> + bool shrinking_slab)
> {
> - unsigned long nr_slab;
> + unsigned long nr_slab = 0;
> struct reclaim_state *reclaim_state = current->reclaim_state;
> struct shrink_control shrink = {
> .gfp_mask = sc->gfp_mask,
> @@ -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;
> @@ -2713,6 +2720,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
> int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
> unsigned long nr_soft_reclaimed;
> unsigned long nr_soft_scanned;
> + bool shrinking_slab = true;
> struct scan_control sc = {
> .gfp_mask = GFP_KERNEL,
> .priority = DEF_PRIORITY,
> @@ -2861,7 +2869,8 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
> * already being scanned that that high
> * watermark would be met at 100% efficiency.
> */
> - if (kswapd_shrink_zone(zone, &sc, lru_pages))
> + if (kswapd_shrink_zone(zone, &sc,
> + lru_pages, shrinking_slab))
> raise_priority = false;
>
> nr_to_reclaim += sc.nr_to_reclaim;
> @@ -2900,6 +2909,9 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
> pfmemalloc_watermark_ok(pgdat))
> wake_up(&pgdat->pfmemalloc_wait);
>
> + /* Only shrink slab once per priority */
> + shrinking_slab = false;
> +
> /*
> * Fragmentation may mean that the system cannot be rebalanced
> * for high-order allocations in all zones. If twice the
> @@ -2925,8 +2937,10 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
> * Raise priority if scanning rate is too low or there was no
> * progress in reclaiming pages
> */
> - if (raise_priority || !this_reclaimed)
> + if (raise_priority || !this_reclaimed) {
> sc.priority--;
> + shrinking_slab = true;
> + }
> } while (sc.priority >= 1 &&
> !pgdat_balanced(pgdat, order, *classzone_idx));
>
> --
> 1.8.1.4
>
--
Michal Hocko
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>