From: Wonhyuk Yang <vvghjk1234@xxxxxxxxx>
Subject: mm/compaction: fix 'limit' in fast_isolate_freepages
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
Link: https://lkml.kernel.org/r/20210626082443.22547-1-vvghjk1234@xxxxxxxxx
Fixes: 5a811889de10f ("mm, compaction: use free lists to quickly locate a migration target")
Signed-off-by: Wonhyuk Yang <vvghjk1234@xxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/mm/compaction.c~mm-compaction-fix-limit-in-fast_isolate_freepages
+++ a/mm/compaction.c
@@ -1378,7 +1378,7 @@ static int next_search_order(struct comp
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;
@@ -1490,11 +1490,11 @@ fast_isolate_freepages(struct compact_co
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) {
_
