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authorJohannes Weiner <hannes@cmpxchg.org>2013-02-22 16:32:12 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2013-02-23 17:50:09 -0800
commitd778df51c09264076fe0208c099ef7d428f21790 (patch)
tree8022d838d72a46c23736218c460714652282a6db /mm/vmscan.c
parent7c5bd705d8f983ae1868a126956f5aa3a6702e3f (diff)
downloadlinux-d778df51c09264076fe0208c099ef7d428f21790.tar.bz2
mm: vmscan: save work scanning (almost) empty LRU lists
In certain cases (kswapd reclaim, memcg target reclaim), a fixed minimum amount of pages is scanned from the LRU lists on each iteration, to make progress. Do not make this minimum bigger than the respective LRU list size, however, and save some busy work trying to isolate and reclaim pages that are not there. Empty LRU lists are quite common with memory cgroups in NUMA environments because there exists a set of LRU lists for each zone for each memory cgroup, while the memory of a single cgroup is expected to stay on just one node. The number of expected empty LRU lists is thus memcgs * (nodes - 1) * lru types Each attempt to reclaim from an empty LRU list does expensive size comparisons between lists, acquires the zone's lru lock etc. Avoid that. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Rik van Riel <riel@redhat.com> Acked-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Michal Hocko <mhocko@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: Satoru Moriya <satoru.moriya@hds.com> Cc: Simon Jeons <simon.jeons@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmscan.c')
-rw-r--r--mm/vmscan.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index ff842d9a7714..e4521ba1ddd0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1761,15 +1761,17 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
out:
for_each_evictable_lru(lru) {
int file = is_file_lru(lru);
+ unsigned long size;
unsigned long scan;
- scan = get_lru_size(lruvec, lru);
+ size = get_lru_size(lruvec, lru);
if (sc->priority || noswap || !vmscan_swappiness(sc)) {
- scan >>= sc->priority;
+ scan = size >> sc->priority;
if (!scan && force_scan)
- scan = SWAP_CLUSTER_MAX;
+ scan = min(size, SWAP_CLUSTER_MAX);
scan = div64_u64(scan * fraction[file], denominator);
- }
+ } else
+ scan = size;
nr[lru] = scan;
}
}