balance_pgdat() is very long and some of the logic can and should
be internal to kswapd_shrink_zone(). Move it so the flow of
balance_pgdat() is marginally easier to follow.
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
mm/vmscan.c | 110 +++++++++++++++++++++++++++++-------------------------------
1 file changed, 54 insertions(+), 56 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index e65fe46..0ba9d3a 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2705,18 +2705,53 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
* This is used to determine if the scanning priority needs to be raised.
*/
static bool kswapd_shrink_zone(struct zone *zone,
+ int classzone_idx,
struct scan_control *sc,
unsigned long lru_pages,
unsigned long *nr_attempted)
{
unsigned long nr_slab;
+ int testorder = sc->order;
+ unsigned long balance_gap;
struct reclaim_state *reclaim_state = current->reclaim_state;
struct shrink_control shrink = {
.gfp_mask = sc->gfp_mask,
};
+ bool lowmem_pressure;
/* Reclaim above the high watermark. */
sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone));
+
+ /*
+ * Kswapd reclaims only single pages with compaction enabled. Trying
+ * too hard to reclaim until contiguous free pages have become
+ * available can hurt performance by evicting too much useful data
+ * from memory. Do not reclaim more than needed for compaction.
+ */
+ if (IS_ENABLED(CONFIG_COMPACTION) && sc->order &&
+ compaction_suitable(zone, sc->order) !=
+ COMPACT_SKIPPED)
+ testorder = 0;
+
+ /*
+ * We put equal pressure on every zone, unless one zone has way too
+ * many pages free already. The "too many pages" is defined as the
+ * high wmark plus a "gap" where the gap is either the low
+ * watermark or 1% of the zone, whichever is smaller.
+ */
+ balance_gap = min(low_wmark_pages(zone),
+ (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
+ KSWAPD_ZONE_BALANCE_GAP_RATIO);
+
+ /*
+ * If there is no low memory pressure or the zone is balanced then no
+ * reclaim is necessary
+ */
+ lowmem_pressure = (buffer_heads_over_limit && is_highmem(zone));
+ if (!lowmem_pressure && zone_balanced(zone, testorder,
+ balance_gap, classzone_idx))
+ return true;
+
shrink_zone(zone, sc);
reclaim_state->reclaimed_slab = 0;
@@ -2731,6 +2766,18 @@ static bool kswapd_shrink_zone(struct zone *zone,
zone_clear_flag(zone, ZONE_WRITEBACK);
+ /*
+ * If a zone reaches its high watermark, consider it to be no longer
+ * congested. It's possible there are dirty pages backed by congested
+ * BDIs but as pressure is relieved, speculatively avoid congestion
+ * waits.
+ */
+ if (!zone->all_unreclaimable &&
+ zone_balanced(zone, testorder, 0, classzone_idx)) {
+ zone_clear_flag(zone, ZONE_CONGESTED);
+ zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY);
+ }
+
return sc->nr_scanned >= sc->nr_to_reclaim;
}
@@ -2866,8 +2913,6 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
*/
for (i = 0; i <= end_zone; i++) {
struct zone *zone = pgdat->node_zones + i;
- int testorder;
- unsigned long balance_gap;
if (!populated_zone(zone))
continue;
@@ -2888,61 +2933,14 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
sc.nr_reclaimed += nr_soft_reclaimed;
/*
- * We put equal pressure on every zone, unless
- * one zone has way too many pages free
- * already. The "too many pages" is defined
- * as the high wmark plus a "gap" where the
- * gap is either the low watermark or 1%
- * of the zone, whichever is smaller.
- */
- balance_gap = min(low_wmark_pages(zone),
- (zone->managed_pages +
- KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
- KSWAPD_ZONE_BALANCE_GAP_RATIO);
- /*
- * Kswapd reclaims only single pages with compaction
- * enabled. Trying too hard to reclaim until contiguous
- * free pages have become available can hurt performance
- * by evicting too much useful data from memory.
- * Do not reclaim more than needed for compaction.
+ * There should be no need to raise the scanning
+ * priority if enough pages are already being scanned
+ * that that high watermark would be met at 100%
+ * efficiency.
*/
- testorder = order;
- if (IS_ENABLED(CONFIG_COMPACTION) && order &&
- compaction_suitable(zone, order) !=
- COMPACT_SKIPPED)
- testorder = 0;
-
- if ((buffer_heads_over_limit && is_highmem_idx(i)) ||
- !zone_balanced(zone, testorder,
- balance_gap, end_zone)) {
- /*
- * There should be no need to raise the
- * scanning priority if enough pages are
- * already being scanned that high
- * watermark would be met at 100% efficiency.
- */
- if (kswapd_shrink_zone(zone, &sc, lru_pages,
- &nr_attempted))
- raise_priority = false;
- }
-
- if (zone->all_unreclaimable) {
- if (end_zone && end_zone == i)
- end_zone--;
- continue;
- }
-
- if (zone_balanced(zone, testorder, 0, end_zone))
- /*
- * If a zone reaches its high watermark,
- * consider it to be no longer congested. It's
- * possible there are dirty pages backed by
- * congested BDIs but as pressure is relieved,
- * speculatively avoid congestion waits
- * or writing pages from kswapd context.
- */
- zone_clear_flag(zone, ZONE_CONGESTED);
- zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY);
+ if (kswapd_shrink_zone(zone, end_zone, &sc,
+ lru_pages, &nr_attempted))
+ raise_priority = false;
}
/*
--
1.8.1.4
--
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>