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authorMel Gorman <mel@csn.ul.ie>2009-06-16 15:33:22 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 19:47:45 -0700
commitfa5e084e43eb14c14942027e1e2e894aeed96097 (patch)
tree3e7ebf714858e8dd1de7042fd1ef62294a3ec20f /mm
parent90afa5de6f3fa89a733861e843377302479fcf7e (diff)
downloadlinux-fa5e084e43eb14c14942027e1e2e894aeed96097.tar.gz
vmscan: do not unconditionally treat zones that fail zone_reclaim() as full
On NUMA machines, the administrator can configure zone_reclaim_mode that is a more targetted form of direct reclaim. On machines with large NUMA distances for example, a zone_reclaim_mode defaults to 1 meaning that clean unmapped pages will be reclaimed if the zone watermarks are not being met. The problem is that zone_reclaim() failing at all means the zone gets marked full. This can cause situations where a zone is usable, but is being skipped because it has been considered full. Take a situation where a large tmpfs mount is occuping a large percentage of memory overall. The pages do not get cleaned or reclaimed by zone_reclaim(), but the zone gets marked full and the zonelist cache considers them not worth trying in the future. This patch makes zone_reclaim() return more fine-grained information about what occured when zone_reclaim() failued. The zone only gets marked full if it really is unreclaimable. If it's a case that the scan did not occur or if enough pages were not reclaimed with the limited reclaim_mode, then the zone is simply skipped. There is a side-effect to this patch. Currently, if zone_reclaim() successfully reclaimed SWAP_CLUSTER_MAX, an allocation attempt would go ahead. With this patch applied, zone watermarks are rechecked after zone_reclaim() does some work. This bug was introduced by commit 9276b1bc96a132f4068fdee00983c532f43d3a26 ("memory page_alloc zonelist caching speedup") way back in 2.6.19 when the zonelist_cache was introduced. It was not intended that zone_reclaim() aggressively consider the zone to be full when it failed as full direct reclaim can still be an option. Due to the age of the bug, it should be considered a -stable candidate. Signed-off-by: Mel Gorman <mel@csn.ul.ie> Reviewed-by: Wu Fengguang <fengguang.wu@intel.com> Reviewed-by: Rik van Riel <riel@redhat.com> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/internal.h4
-rw-r--r--mm/page_alloc.c26
-rw-r--r--mm/vmscan.c11
3 files changed, 32 insertions, 9 deletions
diff --git a/mm/internal.h b/mm/internal.h
index f02c7508068..f290c4db528 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -259,4 +259,8 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, int len, int flags,
struct page **pages, struct vm_area_struct **vmas);
+#define ZONE_RECLAIM_NOSCAN -2
+#define ZONE_RECLAIM_FULL -1
+#define ZONE_RECLAIM_SOME 0
+#define ZONE_RECLAIM_SUCCESS 1
#endif
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6407cbfccd7..2f457a756d4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1462,15 +1462,33 @@ zonelist_scan:
BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK);
if (!(alloc_flags & ALLOC_NO_WATERMARKS)) {
unsigned long mark;
+ int ret;
+
mark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
- if (!zone_watermark_ok(zone, order, mark,
- classzone_idx, alloc_flags)) {
- if (!zone_reclaim_mode ||
- !zone_reclaim(zone, gfp_mask, order))
+ if (zone_watermark_ok(zone, order, mark,
+ classzone_idx, alloc_flags))
+ goto try_this_zone;
+
+ if (zone_reclaim_mode == 0)
+ goto this_zone_full;
+
+ ret = zone_reclaim(zone, gfp_mask, order);
+ switch (ret) {
+ case ZONE_RECLAIM_NOSCAN:
+ /* did not scan */
+ goto try_next_zone;
+ case ZONE_RECLAIM_FULL:
+ /* scanned but unreclaimable */
+ goto this_zone_full;
+ default:
+ /* did we reclaim enough */
+ if (!zone_watermark_ok(zone, order, mark,
+ classzone_idx, alloc_flags))
goto this_zone_full;
}
}
+try_this_zone:
page = buffered_rmqueue(preferred_zone, zone, order,
gfp_mask, migratetype);
if (page)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 79a98d98ed3..16c82a868e2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2492,16 +2492,16 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
*/
if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
- return 0;
+ return ZONE_RECLAIM_FULL;
if (zone_is_all_unreclaimable(zone))
- return 0;
+ return ZONE_RECLAIM_FULL;
/*
* Do not scan if the allocation should not be delayed.
*/
if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
- return 0;
+ return ZONE_RECLAIM_NOSCAN;
/*
* Only run zone reclaim on the local zone or on zones that do not
@@ -2511,10 +2511,11 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
*/
node_id = zone_to_nid(zone);
if (node_state(node_id, N_CPU) && node_id != numa_node_id())
- return 0;
+ return ZONE_RECLAIM_NOSCAN;
if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
- return 0;
+ return ZONE_RECLAIM_NOSCAN;
+
ret = __zone_reclaim(zone, gfp_mask, order);
zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);