From d773ed6b856a96bd6d18b6e04455e3ced0876da4 Mon Sep 17 00:00:00 2001
From: David Rientjes <rientjes@google.com>
Date: Tue, 16 Oct 2007 23:26:01 -0700
Subject: [PATCH] mm: test and set zone reclaim lock before starting reclaim
Introduces new zone flag interface for testing and setting flags:
int zone_test_and_set_flag(struct zone *zone, zone_flags_t flag)
Instead of setting and clearing ZONE_RECLAIM_LOCKED each time shrink_zone() is
called, this flag is test and set before starting zone reclaim. Zone reclaim
starts in __alloc_pages() when a zone's watermark fails and the system is in
zone_reclaim_mode. If it's already in reclaim, there's no need to start again
so it is simply considered full for that allocation attempt.
There is a change of behavior with regard to concurrent zone shrinking. It is
now possible for try_to_free_pages() or kswapd to already be shrinking a
particular zone when __alloc_pages() starts zone reclaim. In this case, it is
possible for two concurrent threads to invoke shrink_zone() for a single zone.
This change forbids a zone to be in zone reclaim twice, which was always the
behavior, but allows for concurrent try_to_free_pages() or kswapd shrinking
when starting zone reclaim.
Cc: Andrea Arcangeli <andrea@suse.de>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/mmzone.h | 8 ++++++++
mm/vmscan.c | 23 +++++++++++++----------
2 files changed, 21 insertions(+), 10 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 9011505e740..4c4522a51a3 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -351,6 +351,12 @@ static inline void zone_set_flag(struct zone *zone, zone_flags_t flag)
{
set_bit(flag, &zone->flags);
}
+
+static inline int zone_test_and_set_flag(struct zone *zone, zone_flags_t flag)
+{
+ return test_and_set_bit(flag, &zone->flags);
+}
+
static inline void zone_clear_flag(struct zone *zone, zone_flags_t flag)
{
clear_bit(flag, &zone->flags);
@@ -360,10 +366,12 @@ static inline int zone_is_all_unreclaimable(const struct zone *zone)
{
return test_bit(ZONE_ALL_UNRECLAIMABLE, &zone->flags);
}
+
static inline int zone_is_reclaim_locked(const struct zone *zone)
{
return test_bit(ZONE_RECLAIM_LOCKED, &zone->flags);
}
+
static inline int zone_is_oom_locked(const struct zone *zone)
{
return test_bit(ZONE_OOM_LOCKED, &zone->flags);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index d8893dc2d4e..e1471385d00 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1108,8 +1108,6 @@ static unsigned long shrink_zone(int priority, struct zone *zone,
unsigned long nr_to_scan;
unsigned long nr_reclaimed = 0;
- zone_set_flag(zone, ZONE_RECLAIM_LOCKED);
-
/*
* Add one to `nr_to_scan' just to make sure that the kernel will
* slowly sift through the active list.
@@ -1148,8 +1146,6 @@ static unsigned long shrink_zone(int priority, struct zone *zone,
}
throttle_vm_writeout(sc->gfp_mask);
-
- zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
return nr_reclaimed;
}
@@ -1900,6 +1896,7 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
{
int node_id;
+ int ret;
/*
* Zone reclaim reclaims unmapped file backed pages and
@@ -1917,13 +1914,13 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
<= zone->min_slab_pages)
return 0;
+ if (zone_is_all_unreclaimable(zone))
+ return 0;
+
/*
- * Avoid concurrent zone reclaims, do not reclaim in a zone that does
- * not have reclaimable pages and if we should not delay the allocation
- * then do not scan.
+ * Do not scan if the allocation should not be delayed.
*/
- if (!(gfp_mask & __GFP_WAIT) || zone_is_all_unreclaimable(zone) ||
- zone_is_reclaim_locked(zone) || (current->flags & PF_MEMALLOC))
+ if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
return 0;
/*
@@ -1935,6 +1932,12 @@ 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(zone, gfp_mask, order);
+
+ if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
+ return 0;
+ ret = __zone_reclaim(zone, gfp_mask, order);
+ zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
+
+ return ret;
}
#endif
--
2.20.1