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Date: Mon, 8 Jun 2009 14:01:30 +0100
From: Mel Gorman <mel@....ul.ie>
To: Mel Gorman <mel@....ul.ie>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Rik van Riel <riel@...hat.com>,
Christoph Lameter <cl@...ux-foundation.org>,
yanmin.zhang@...el.com, Wu Fengguang <fengguang.wu@...el.com>,
linuxram@...ibm.com
Cc: linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 3/3] 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.
Signed-off-by: Mel Gorman <mel@....ul.ie>
---
mm/internal.h | 4 ++++
mm/page_alloc.c | 26 ++++++++++++++++++++++----
mm/vmscan.c | 10 +++++-----
3 files changed, 31 insertions(+), 9 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index 987bb03..090c267 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -284,4 +284,8 @@ 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 fe753ec..ce2f684 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1420,20 +1420,38 @@ zonelist_scan:
if (!(alloc_flags & ALLOC_NO_WATERMARKS)) {
unsigned long mark;
+ int ret;
if (alloc_flags & ALLOC_WMARK_MIN)
mark = zone->pages_min;
else if (alloc_flags & ALLOC_WMARK_LOW)
mark = zone->pages_low;
else
mark = zone->pages_high;
- 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 try_next_zone;
}
}
+try_this_zone:
page = buffered_rmqueue(preferred_zone, zone, order, gfp_mask);
if (page)
break;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index ffe2f32..84cdae2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2409,7 +2409,7 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
if (pagecache_reclaimable <= zone->min_unmapped_pages
&& zone_page_state(zone, NR_SLAB_RECLAIMABLE)
<= zone->min_slab_pages)
- return 0;
+ return ZONE_RECLAIM_NOSCAN;
/* Do not attempt a scan if scanning failed recently */
if (time_before(jiffies,
@@ -2417,13 +2417,13 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
return 0;
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
@@ -2433,10 +2433,10 @@ 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);
--
1.5.6.5
--
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