In small high zone(ex, 40M movable zone), reclaim priority
could be raised easily so congestion_wait of balance_pgdat can make
kswapd sleep unnecessarily so process ends up entering into direct
reclaim path. It means processes's latency would be longer.
This patch changes congestion_wait with wait_iff_congested so kswapd
will sleep only if backdev really is congested.
==DRIVER mapped-file-stream mapped-file-stream(0.00, -nan%)
Name mapped-file-stream mapped-file-stream(0.00, -nan%)
Elapsed 676 663 (-13.00, -1.92%)
nr_vmscan_write 91 1341 (1250.00, 1373.63%)
nr_vmscan_immediate_reclaim 0 0 (0.00, 0.00%)
pgpgin 29932 21668 (-8264.00,-27.61%)
pgpgout 3652 8392 (4740.00, 129.79%)
pswpin 0 22 (22.00, 0.00%)
pswpout 91 1341 (1250.00, 1373.63%)
pgactivate 15686 16217 (531.00, 3.39%)
pgdeactivate 14171 15431 (1260.00, 8.89%)
pgfault 204523237 204524355 (1118.00, 0.00%)
pgmajfault 204472586 204472528 (-58.00, -0.00%)
pgsteal_kswapd_dma 149066 466676 (317610.00,213.07%)
pgsteal_kswapd_normal 56219654 49663877 (-6555777.00,-11.66%)
pgsteal_kswapd_high 92860817 138182330 (45321513.00,48.81%)
pgsteal_kswapd_movable 1211389 4236726 (3025337.00,249.74%)
pgsteal_direct_dma 35808 9306 (-26502.00,-74.01%)
pgsteal_direct_normal 21270282 123835 (-21146447.00,-99.42%)
pgsteal_direct_high 21051650 274887 (-20776763.00,-98.69%)
pgsteal_direct_movable 250572 38011 (-212561.00,-84.83%)
pgscan_kswapd_dma 325126 947813 (622687.00,191.52%)
pgscan_kswapd_normal 111171753 97902722 (-13269031.00,-11.94%)
pgscan_kswapd_high 178149789 274337809 (96188020.00,53.99%)
pgscan_kswapd_movable 2537926 8496474 (5958548.00,234.78%)
pgscan_direct_dma 56919 22855 (-34064.00,-59.85%)
pgscan_direct_normal 45698152 3604954 (-42093198.00,-92.11%)
pgscan_direct_high 51326549 4504909 (-46821640.00,-91.22%)
pgscan_direct_movable 433830 105418 (-328412.00,-75.70%)
pgscan_direct_throttle 0 0 (0.00, 0.00%)
pginodesteal 6721 11111 (4390.00, 65.32%)
slabs_scanned 57344 56320 (-1024.00,-1.79%)
kswapd_inodesteal 36327 31121 (-5206.00,-14.33%)
kswapd_low_wmark_hit_quickly 533 4607 (4074.00, 764.35%)
kswapd_high_wmark_hit_quickly 39 432 (393.00, 1007.69%)
kswapd_skip_congestion_wait 71505 10254 (-61251.00,-85.66%)
pageoutrun 2406110 2879697 (473587.00,19.68%)
allocstall 696424 8222 (-688202.00,-98.82%)
pgrotated 91 1341 (1250.00, 1373.63%)
kswapd_totalscan 292184594 381684818 (89500224.00,30.63%)
kswapd_totalsteal 150440926 192549609 (42108683.00,27.99%)
Kswapd_efficiency 51.00 50.00 (-1.00, -1.96%)
direct_totalscan 97515450 8238136 (-89277314.00,-91.55%)
direct_totalsteal 42608312 446039 (-42162273.00,-98.95%)
direct_efficiency 43.00 5.00 (-38.00, -88.37%)
reclaim_velocity 576479.35 588119.08 (11639.73,2.02%)
Elapsed time of test program is reduced by 13 second.
As I expected, kswapd scanning/reclaim ratio is increased about 30%
but kswapd's efficiency is still good. We reduced allocstall about 98%
so I think it's most important factor for reducing elapsed time of
test program.
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
mm/vmscan.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index f015d92..d1ebe69 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2705,8 +2705,16 @@ loop_again:
if (total_scanned && (sc.priority < DEF_PRIORITY - 2)) {
if (has_under_min_watermark_zone)
count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
- else
- congestion_wait(BLK_RW_ASYNC, HZ/10);
+ else {
+ for (i = 0; i <= end_zone; i++) {
+ struct zone *zone = pgdat->node_zones
+ + i;
+ if (!populated_zone(zone))
+ continue;
+ wait_iff_congested(zone, BLK_RW_ASYNC,
+ HZ/10);
+ }
+ }
}
/*
--
1.7.9.5
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