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authorSatoru Moriya <satoru.moriya@hds.com>2012-05-29 15:06:47 -0700
committerBen Hutchings <ben@decadent.org.uk>2012-09-12 03:37:37 +0100
commita65afe79af5181ca0fca10262908738b4f453b97 (patch)
tree5df56b2ef2aa0de3b48646fa1dbe8d6e4329f8f1
parent4bddad580a7b4d023a981e2cbdf0c9e3837f6505 (diff)
mm: avoid swapping out with swappiness==0
commit fe35004fbf9eaf67482b074a2e032abb9c89b1dd upstream. Sometimes we'd like to avoid swapping out anonymous memory. In particular, avoid swapping out pages of important process or process groups while there is a reasonable amount of pagecache on RAM so that we can satisfy our customers' requirements. OTOH, we can control how aggressive the kernel will swap memory pages with /proc/sys/vm/swappiness for global and /sys/fs/cgroup/memory/memory.swappiness for each memcg. But with current reclaim implementation, the kernel may swap out even if we set swappiness=0 and there is pagecache in RAM. This patch changes the behavior with swappiness==0. If we set swappiness==0, the kernel does not swap out completely (for global reclaim until the amount of free pages and filebacked pages in a zone has been reduced to something very very small (nr_free + nr_filebacked < high watermark)). Signed-off-by: Satoru Moriya <satoru.moriya@hds.com> Acked-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Rik van Riel <riel@redhat.com> Acked-by: Jerome Marchand <jmarchan@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [bwh: Backported to 3.2: - Adjust context - vmscan_swappiness() does not have a zone parameter] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
-rw-r--r--mm/vmscan.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 48febd7ce9be..86eb848259a9 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1977,10 +1977,10 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc,
* proportional to the fraction of recently scanned pages on
* each list that were recently referenced and in active use.
*/
- ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
+ ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
ap /= reclaim_stat->recent_rotated[0] + 1;
- fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
+ fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
fp /= reclaim_stat->recent_rotated[1] + 1;
spin_unlock_irq(&zone->lru_lock);
@@ -1993,7 +1993,7 @@ out:
unsigned long scan;
scan = zone_nr_lru_pages(zone, sc, l);
- if (priority || noswap) {
+ if (priority || noswap || !vmscan_swappiness(sc)) {
scan >>= priority;
if (!scan && force_scan)
scan = SWAP_CLUSTER_MAX;