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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 84b18490d1.

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>
This commit is contained in:
KOSAKI Motohiro 2010-04-06 14:34:56 -07:00 committed by Linus Torvalds
parent 6e191f7bb0
commit d6da1a5abc
1 changed files with 9 additions and 14 deletions
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23
mm/vmscan.c
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@ -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;
get_scan_ratio(zone, sc, percent);
/* 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;
}