Commit d6da1a5a authored Apr 06, 2010 by KOSAKI Motohiro Committed by Linus Torvalds Apr 07, 2010

mm: revert "vmscan: get_scan_ratio() cleanup"



Shaohua Li reported his tmpfs streaming I/O test can lead to make oom.
The test uses a 6G tmpfs in a system with 3G memory.  In the tmpfs, there
are 6 copies of kernel source and the test does kbuild for each copy.  His
investigation shows the test has a lot of rotated anon pages and quite few
file pages, so get_scan_ratio calculates percent[0] (i.e.  scanning
percent for anon) to be zero.  Actually the percent[0] shoule be a big
value, but our calculation round it to zero.

Although before commit 84b18490 ("vmscan: get_scan_ratio() cleanup") , we
have the same problem too.  But the old logic can rescue percent[0]==0
case only when priority==0.  It had hided the real issue.  I didn't think
merely streaming io can makes percent[0]==0 && priority==0 situation.  but
I was wrong.

So, definitely we have to fix such tmpfs streaming io issue.  but anyway I
revert the regression commit at first.

This reverts commit 84b18490.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reported-by: Shaohua Li <shaohua.li@intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 6e191f7b

mm/vmscan.c

+9 −14

Original line number	Diff line number	Diff line
		@@ -1535,13 +1535,6 @@ static void get_scan_ratio(struct zone zone, struct scan_control sc,
		unsigned long ap, fp;
		struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);

		/* If we have no swap space, do not bother scanning anon pages. */
		if (!sc->may_swap \|\| (nr_swap_pages <= 0)) {
		percent[0] = 0;
		percent[1] = 100;
		return;
		}

		anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
		zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
		file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
		@@ -1639,20 +1632,22 @@ static void shrink_zone(int priority, struct zone *zone,
		unsigned long nr_reclaimed = sc->nr_reclaimed;
		unsigned long nr_to_reclaim = sc->nr_to_reclaim;
		struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
		int noswap = 0;

		/* If we have no swap space, do not bother scanning anon pages. */
		if (!sc->may_swap \|\| (nr_swap_pages <= 0)) {
		noswap = 1;
		percent[0] = 0;
		percent[1] = 100;
		} else
		get_scan_ratio(zone, sc, percent);

		for_each_evictable_lru(l) {
		int file = is_file_lru(l);
		unsigned long scan;

		if (percent[file] == 0) {
		nr[l] = 0;
		continue;
		}

		scan = zone_nr_lru_pages(zone, sc, l);
		if (priority) {
		if (priority \|\| noswap) {
		scan >>= priority;
		scan = (scan * percent[file]) / 100;
		}

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