When built with CONFIG_COMPACTION, kswapd does not try to free
contiguous pages. Because it is not trying, it should also not
test whether it succeeded, because that can result in continuous
page reclaim, until a large fraction of memory is free and large
fractions of the working set have been evicted.
Also remove a line of code that increments balanced right before
exiting the function.
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
---
mm/vmscan.c | 22 +++++++++++++++++-----
1 files changed, 17 insertions(+), 5 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index f54a05b..c3eec6b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2608,7 +2608,7 @@ loop_again:
*/
for (i = 0; i <= end_zone; i++) {
struct zone *zone = pgdat->node_zones + i;
- int nr_slab;
+ int nr_slab, testorder;
unsigned long balance_gap;
if (!populated_zone(zone))
@@ -2637,11 +2637,25 @@ loop_again:
* gap is either the low watermark or 1%
* of the zone, whichever is smaller.
*/
+ testorder = order;
balance_gap = min(low_wmark_pages(zone),
(zone->present_pages +
KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
KSWAPD_ZONE_BALANCE_GAP_RATIO);
- if (!zone_watermark_ok_safe(zone, order,
+ /*
+ * Kswapd reclaims only single pages when
+ * COMPACTION_BUILD. Trying too hard to get
+ * contiguous free pages can result in excessive
+ * amounts of free memory, and useful things
+ * getting kicked out of memory.
+ * Limit the amount of reclaim to something sane,
+ * plus space for compaction to do its thing.
+ */
+ if (COMPACTION_BUILD) {
+ testorder = 0;
+ balance_gap += 2<<order;
+ }
+ if (!zone_watermark_ok_safe(zone, testorder,
high_wmark_pages(zone) + balance_gap,
end_zone, 0)) {
shrink_zone(priority, zone, &sc);
@@ -2670,7 +2684,7 @@ loop_again:
continue;
}
- if (!zone_watermark_ok_safe(zone, order,
+ if (!zone_watermark_ok_safe(zone, testorder,
high_wmark_pages(zone), end_zone, 0)) {
all_zones_ok = 0;
/*
@@ -2776,8 +2790,6 @@ out:
/* If balanced, clear the congested flag */
zone_clear_flag(zone, ZONE_CONGESTED);
- if (i <= *classzone_idx)
- balanced += zone->present_pages;
}
}
--
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