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Message-Id: <1244717273-15176-3-git-send-email-mel@csn.ul.ie>
Date: Thu, 11 Jun 2009 11:47:52 +0100
From: Mel Gorman <mel@....ul.ie>
To: Mel Gorman <mel@....ul.ie>,
Andrew Morton <akpm@...ux-foundation.org>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: Rik van Riel <riel@...hat.com>,
Christoph Lameter <cl@...ux-foundation.org>,
Wu Fengguang <fengguang.wu@...el.com>, linuxram@...ibm.com,
linux-mm <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/3] 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>
Reviewed-by: Wu Fengguang <fengguang.wu@...el.com>
Reviewed-by: Rik van Riel <riel@...hat.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
---
mm/internal.h | 4 ++++
mm/page_alloc.c | 26 ++++++++++++++++++++++----
mm/vmscan.c | 11 ++++++-----
3 files changed, 32 insertions(+), 9 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index f02c750..f290c4d 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 d35e753..667ffbb 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1477,15 +1477,33 @@ 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 d832ba8..7b8eb3f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2465,16 +2465,16 @@ 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
@@ -2484,10 +2484,11 @@ 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);
--
1.5.6.5
--
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