Because of 'min(1, ...)', fast_isolate_freepages set 'limit'
to 0 or 1. This takes away the opportunities of find candinate
pages. So, by making enough scans available, increases the
probability of finding the appropriate freepage.
Tested it on the thpscale and the results are as follows.
5.12.0 5.12.0
valnilla patched
Amean fault-both-1 598.15 ( 0.00%) 592.56 ( 0.93%)
Amean fault-both-3 1494.47 ( 0.00%) 1514.35 ( -1.33%)
Amean fault-both-5 2519.48 ( 0.00%) 2471.76 ( 1.89%)
Amean fault-both-7 3173.85 ( 0.00%) 3079.19 ( 2.98%)
Amean fault-both-12 8063.83 ( 0.00%) 7858.29 ( 2.55%)
Amean fault-both-18 8781.20 ( 0.00%) 7827.70 * 10.86%*
Amean fault-both-24 12576.44 ( 0.00%) 12250.20 ( 2.59%)
Amean fault-both-30 18503.27 ( 0.00%) 17528.11 * 5.27%*
Amean fault-both-32 16133.69 ( 0.00%) 13874.24 * 14.00%*
5.12.0 5.12.0
vanilla patched
Ops Compaction migrate scanned 6547133.00 5963901.00
Ops Compaction free scanned 32452453.00 26609101.00
5.12 5.12
vanilla patched
Duration User 27.99 28.84
Duration System 244.08 236.76
Duration Elapsed 78.27 78.38
Fixes: 5a811889de10f ("mm, compaction: use free lists to quickly locate a migration target")
Signed-off-by: Wonhyuk Yang <vvghjk1234@xxxxxxxxx>
---
mm/compaction.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 84fde270ae74..12d5b5a86078 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1380,7 +1380,7 @@ static int next_search_order(struct compact_control *cc, int order)
static unsigned long
fast_isolate_freepages(struct compact_control *cc)
{
- unsigned int limit = min(1U, freelist_scan_limit(cc) >> 1);
+ unsigned int limit = max(1U, freelist_scan_limit(cc) >> 1);
unsigned int nr_scanned = 0;
unsigned long low_pfn, min_pfn, highest = 0;
unsigned long nr_isolated = 0;
@@ -1492,11 +1492,11 @@ fast_isolate_freepages(struct compact_control *cc)
spin_unlock_irqrestore(&cc->zone->lock, flags);
/*
- * Smaller scan on next order so the total scan ig related
+ * Smaller scan on next order so the total scan is related
* to freelist_scan_limit.
*/
if (order_scanned >= limit)
- limit = min(1U, limit >> 1);
+ limit = max(1U, limit >> 1);
}
if (!page) {
--
2.30.2
