From 3328d7706e5f3cf40e34ec5a2e36ee5e7bd05191 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Thu, 25 Aug 2011 09:46:54 +1000 Subject: [PATCH] The nr_force_scan[] tuple holds the effective scan numbers for anon and file pages in case the situation called for a forced scan and the regularly calculated scan numbers turned out zero. However, the effective scan number can always be assumed to be SWAP_CLUSTER_MAX right before the division into anon and file. The numerators and denominator are properly set up for all cases, be it force scan for just file, just anon, or both, to do the right thing. Signed-off-by: Johannes Weiner Reviewed-by: Minchan Kim Acked-by: KAMEZAWA Hiroyuki Reviewed-by: Michal Hocko Cc: Ying Han Cc: Balbir Singh Cc: KOSAKI Motohiro Cc: Daisuke Nishimura Acked-by: Mel Gorman Signed-off-by: Andrew Morton --- mm/vmscan.c | 36 ++++++++++++------------------------ 1 file changed, 12 insertions(+), 24 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index b1520b077858..d29b2bdb9e03 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1817,12 +1817,19 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc, enum lru_list l; int noswap = 0; bool force_scan = false; - unsigned long nr_force_scan[2]; - /* kswapd does zone balancing and needs to scan this zone */ + /* + * If the zone or memcg is small, nr[l] can be 0. This + * results in no scanning on this priority and a potential + * priority drop. Global direct reclaim can go to the next + * zone and tends to have no problems. Global kswapd is for + * zone balancing and it needs to scan a minimum amount. When + * reclaiming for a memcg, a priority drop can cause high + * latencies, so it's better to scan a minimum amount there as + * well. + */ if (scanning_global_lru(sc) && current_is_kswapd()) force_scan = true; - /* memcg may have small limit and need to avoid priority drop */ if (!scanning_global_lru(sc)) force_scan = true; @@ -1832,8 +1839,6 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc, fraction[0] = 0; fraction[1] = 1; denominator = 1; - nr_force_scan[0] = 0; - nr_force_scan[1] = SWAP_CLUSTER_MAX; goto out; } @@ -1850,8 +1855,6 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc, fraction[0] = 1; fraction[1] = 0; denominator = 1; - nr_force_scan[0] = SWAP_CLUSTER_MAX; - nr_force_scan[1] = 0; goto out; } } @@ -1900,11 +1903,6 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc, fraction[0] = ap; fraction[1] = fp; denominator = ap + fp + 1; - if (force_scan) { - unsigned long scan = SWAP_CLUSTER_MAX; - nr_force_scan[0] = div64_u64(scan * ap, denominator); - nr_force_scan[1] = div64_u64(scan * fp, denominator); - } out: for_each_evictable_lru(l) { int file = is_file_lru(l); @@ -1913,20 +1911,10 @@ out: scan = zone_nr_lru_pages(zone, sc, l); if (priority || noswap) { scan >>= priority; + if (!scan && force_scan) + scan = SWAP_CLUSTER_MAX; scan = div64_u64(scan * fraction[file], denominator); } - - /* - * If zone is small or memcg is small, nr[l] can be 0. - * This results no-scan on this priority and priority drop down. - * For global direct reclaim, it can visit next zone and tend - * not to have problems. For global kswapd, it's for zone - * balancing and it need to scan a small amounts. When using - * memcg, priority drop can cause big latency. So, it's better - * to scan small amount. See may_noscan above. - */ - if (!scan && force_scan) - scan = nr_force_scan[file]; nr[l] = scan; } } -- 2.39.5