On 03/15/2014 11:36 PM, Hugh Dickins wrote:
From: Suleiman Souhlal <suleiman@xxxxxxxxxx>
Prior to this change, we would decide whether to force scan a LRU
during reclaim if that LRU itself was too small for the current
priority. However, this can lead to the file LRU getting force
scanned even if there are a lot of anonymous pages we can reclaim,
leading to hot file pages getting needlessly reclaimed.
To address this, we instead only force scan when none of the
reclaimable LRUs are big enough.
Gives huge improvements with zswap. For example, when doing -j20
kernel build in a 500MB container with zswap enabled, runtime (in
seconds) is greatly reduced:
x without this change
+ with this change
N Min Max Median Avg Stddev
x 5 700.997 790.076 763.928 754.05 39.59493
+ 5 141.634 197.899 155.706 161.9 21.270224
Difference at 95.0% confidence
-592.15 +/- 46.3521
-78.5293% +/- 6.14709%
(Student's t, pooled s = 31.7819)
Should also give some improvements in regular (non-zswap) swap cases.
Yes, hughd found significant speedup using regular swap, with several
memcgs under pressure; and it should also be effective in the non-memcg
case, whenever one or another zone LRU is forced too small.
Signed-off-by: Suleiman Souhlal <suleiman@xxxxxxxxxx>
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>