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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>
This commit is contained in:
David Rientjes 2007-10-16 23:26:01 -07:00 committed by Linus Torvalds
parent ae74138da6
commit d773ed6b85
2 changed files with 21 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/mmzone.h
View File

@ -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);

23
mm/vmscan.c
View File

@ -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