From: Andrew Morton Date: Fri, 6 Jan 2006 08:11:14 +0000 (-0800) Subject: [PATCH] vmscan: balancing fix X-Git-Tag: v2.6.16-rc1~936^2~246 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=210fe530305ee50cd889fe9250168228b2994f32;p=linux-2.6 [PATCH] vmscan: balancing fix Revert a patch which went into 2.6.8-rc1. The changelog for that patch was: The shrink_zone() logic can, under some circumstances, cause far too many pages to be reclaimed. Say, we're scanning at high priority and suddenly hit a large number of reclaimable pages on the LRU. Change things so we bale out when SWAP_CLUSTER_MAX pages have been reclaimed. Problem is, this change caused significant imbalance in inter-zone scan balancing by truncating scans of larger zones. Suppose, for example, ZONE_HIGHMEM is 10x the size of ZONE_NORMAL. The zone balancing algorithm would require that if we're scanning 100 pages of ZONE_HIGHMEM, we should scan 10 pages of ZONE_NORMAL. But this logic will cause the scanning of ZONE_HIGHMEM to bale out after only 32 pages are reclaimed. Thus effectively causing smaller zones to be scanned relatively harder than large ones. Now I need to remember what the workload was which caused me to write this patch originally, then fix it up in a different way... Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/vmscan.c b/mm/vmscan.c index b2baca7645..5c8a412b43 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -63,9 +63,6 @@ struct scan_control { unsigned long nr_mapped; /* From page_state */ - /* How many pages shrink_cache() should reclaim */ - int nr_to_reclaim; - /* Ask shrink_caches, or shrink_zone to scan at this priority */ unsigned int priority; @@ -656,7 +653,6 @@ static void shrink_cache(struct zone *zone, struct scan_control *sc) if (current_is_kswapd()) mod_page_state(kswapd_steal, nr_freed); mod_page_state_zone(zone, pgsteal, nr_freed); - sc->nr_to_reclaim -= nr_freed; spin_lock_irq(&zone->lru_lock); /* @@ -856,8 +852,6 @@ shrink_zone(struct zone *zone, struct scan_control *sc) else nr_inactive = 0; - sc->nr_to_reclaim = sc->swap_cluster_max; - while (nr_active || nr_inactive) { if (nr_active) { sc->nr_to_scan = min(nr_active, @@ -871,8 +865,6 @@ shrink_zone(struct zone *zone, struct scan_control *sc) (unsigned long)sc->swap_cluster_max); nr_inactive -= sc->nr_to_scan; shrink_cache(zone, sc); - if (sc->nr_to_reclaim <= 0) - break; } }