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authorJohannes Weiner <hannes@cmpxchg.org>2020-06-04 02:02:50 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-04 06:09:48 +0300
commita4fe1631f313f75c7dced10d9e7eda816bf0937f (patch)
tree2b7d803efab7df4552d618bdcc7943b10e94578f /mm/vmscan.c
parent9682468747390c14962114f261cd76ba188ed987 (diff)
downloadlinux-a4fe1631f313f75c7dced10d9e7eda816bf0937f.tar.xz
mm: vmscan: drop unnecessary div0 avoidance rounding in get_scan_count()
When we calculate the relative scan pressure between the anon and file LRU lists, we have to assume that reclaim_stat can contain zeroes. To avoid div0 crashes, we add 1 to all denominators like so: anon_prio = swappiness; file_prio = 200 - anon_prio; [...] /* * The amount of pressure on anon vs file pages is inversely * proportional to the fraction of recently scanned pages on * each list that were recently referenced and in active use. */ ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1); ap /= reclaim_stat->recent_rotated[0] + 1; fp = file_prio * (reclaim_stat->recent_scanned[1] + 1); fp /= reclaim_stat->recent_rotated[1] + 1; spin_unlock_irq(&pgdat->lru_lock); fraction[0] = ap; fraction[1] = fp; denominator = ap + fp + 1; While reclaim_stat can contain 0, it's not actually possible for ap + fp to be 0. One of anon_prio or file_prio could be zero, but they must still add up to 200. And the reclaim_stat fraction, due to the +1 in there, is always at least 1. So if one of the two numerators is 0, the other one can't be. ap + fp is always at least 1. Drop the + 1. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@surriel.com> Link: http://lkml.kernel.org/r/20200520232525.798933-8-hannes@cmpxchg.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmscan.c')
-rw-r--r--mm/vmscan.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c711efc42cfc..a5a7a8d0764c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2348,7 +2348,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
fraction[0] = ap;
fraction[1] = fp;
- denominator = ap + fp + 1;
+ denominator = ap + fp;
out:
for_each_evictable_lru(lru) {
int file = is_file_lru(lru);