mm: vmscan: improve comment on low-page cache handling
Fix comment style and elaborate on why anonymous memory is force-scanned
when file cache runs low.
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>
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 68586c8..259f820 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1713,13 +1713,15 @@
file = get_lru_size(lruvec, LRU_ACTIVE_FILE) +
get_lru_size(lruvec, LRU_INACTIVE_FILE);
+ /*
+ * If it's foreseeable that reclaiming the file cache won't be
+ * enough to get the zone back into a desirable shape, we have
+ * to swap. Better start now and leave the - probably heavily
+ * thrashing - remaining file pages alone.
+ */
if (global_reclaim(sc)) {
- free = zone_page_state(zone, NR_FREE_PAGES);
+ free = zone_page_state(zone, NR_FREE_PAGES);
if (unlikely(file + free <= high_wmark_pages(zone))) {
- /*
- * If we have very few page cache pages, force-scan
- * anon pages.
- */
fraction[0] = 1;
fraction[1] = 0;
denominator = 1;