Hi, I think this should fix the problem of processes getting stuck in reclaim that has been reported several times. Kent actually single-stepped through this code and noted that it was never exiting shrink_zone(), which really narrowed it down a lot, considering the tons of nested loops from the allocator down to the list shrinking. Hannes --- From: Johannes Weiner <hannes@xxxxxxxxxxx> Subject: vmscan: fix zone shrinking exit when scan work is done '3e7d344 mm: vmscan: reclaim order-0 and use compaction instead of lumpy reclaim' introduced an indefinite loop in shrink_zone(). It meant to break out of this loop when no pages had been reclaimed and not a single page was even scanned. The way it would detect the latter is by taking a snapshot of sc->nr_scanned at the beginning of the function and comparing it against the new sc->nr_scanned after the scan loop. But it would re-iterate without updating that snapshot, looping forever if sc->nr_scanned changed at least once since shrink_zone() was invoked. This is not the sole condition that would exit that loop, but it requires other processes to change the zone state, as the reclaimer that is stuck obviously can not anymore. This is only happening for higher-order allocations, where reclaim is run back to back with compaction. Reported-by: Michal Hocko <mhocko@xxxxxxx> Reported-by: Kent Overstreet <kent.overstreet@xxxxxxxxx> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> --- mm/vmscan.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 148c6e6..17497d0 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1882,12 +1882,12 @@ static void shrink_zone(int priority, struct zone *zone, unsigned long nr[NR_LRU_LISTS]; unsigned long nr_to_scan; enum lru_list l; - unsigned long nr_reclaimed; + unsigned long nr_reclaimed, nr_scanned; unsigned long nr_to_reclaim = sc->nr_to_reclaim; - unsigned long nr_scanned = sc->nr_scanned; restart: nr_reclaimed = 0; + nr_scanned = sc->nr_scanned; get_scan_count(zone, sc, nr, priority); while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || -- 1.7.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>