On Sun, 25 Nov 2012 17:57:28 +0100
Johannes Hirte <johannes.hirte@xxxxxxxxxxxxxxxxx> wrote:
> With kernel 3.7-rc6 I've still problems with kswapd0 on my laptop
> And this is most of the time. I've only observed this behavior on the
> laptop. Other systems don't show this.
This suggests it may have something to do with small memory zones,
where we end up with the "funny" situation that the high watermark
(+ balance gap) for a particular zone is less than the low watermark
+ 2<<order pages, which is the number of free pages required to keep
compaction_suitable happy.
Could you try this patch?
---8<---
Subject: mm,vmscan: free pages if compaction_suitable tells us to
For small zones, it is possible for the low watermark + 2<<order pages
to exceed the high watermark + balance_gap. This could send kswapd into
an infinite loop.
The solution is to always free pages if compaction_suitable indicates
we need to do so.
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
---
mm/vmscan.c | 20 ++++++++++----------
1 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 48550c6..b99ecba 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2614,7 +2614,7 @@ 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 nr_slab, testorder;
+ int nr_slab, force_reclaim = 0;
unsigned long balance_gap;
if (!populated_zone(zone))
@@ -2648,21 +2648,21 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
(zone->present_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.
+ * enabled. We reclaim memory if this zone is below
+ * the normal reclaim watermark, or if there is not
+ * enough memory available for compaction.
*/
- testorder = order;
if (COMPACTION_BUILD && order &&
- compaction_suitable(zone, order) !=
+ compaction_suitable(zone, order) ==
COMPACT_SKIPPED)
- testorder = 0;
+ force_reclaim = 1;
if ((buffer_heads_over_limit && is_highmem_idx(i)) ||
- !zone_watermark_ok_safe(zone, testorder,
+ force_reclaim ||
+ !zone_watermark_ok_safe(zone, 0,
high_wmark_pages(zone) + balance_gap,
end_zone, 0)) {
shrink_zone(zone, &sc);
@@ -2691,7 +2691,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
continue;
}
- if (!zone_watermark_ok_safe(zone, testorder,
+ if (!zone_watermark_ok_safe(zone, 0,
high_wmark_pages(zone), end_zone, 0)) {
all_zones_ok = 0;
/*
--
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