At some point slab defragmentation needs to be triggered. The logical
point for this is after slab shrinking was performed in vmscan.c. At
that point the fragmentation ratio of a slab was increased by objects
being freed. So we call kmem_cache_defrag from there.
slab_shrink() from vmscan.c is called in some contexts to do
global shrinking of slabs and in others to do shrinking for
a particular zone. Pass the zone to slab_shrink, so that slab_shrink
can call kmem_cache_defrag() and restrict the defragmentation to
the node that is under memory pressure.
Signed-off-by: Christoph Lameter <[email protected]>
---
fs/drop_caches.c | 2 +-
include/linux/mm.h | 2 +-
include/linux/slab.h | 1 +
mm/vmscan.c | 27 ++++++++++++++++++++-------
4 files changed, 23 insertions(+), 9 deletions(-)
Index: linux-2.6.22-rc6-mm1/include/linux/slab.h
===================================================================
--- linux-2.6.22-rc6-mm1.orig/include/linux/slab.h 2007-07-04 09:53:59.000000000 -0700
+++ linux-2.6.22-rc6-mm1/include/linux/slab.h 2007-07-04 09:56:22.000000000 -0700
@@ -96,6 +96,7 @@ void kmem_cache_free(struct kmem_cache *
unsigned int kmem_cache_size(struct kmem_cache *);
const char *kmem_cache_name(struct kmem_cache *);
int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr);
+int kmem_cache_defrag(int node);
/*
* Please use this macro to create slab caches. Simply specify the
Index: linux-2.6.22-rc6-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.22-rc6-mm1.orig/mm/vmscan.c 2007-07-04 09:53:59.000000000 -0700
+++ linux-2.6.22-rc6-mm1/mm/vmscan.c 2007-07-04 09:59:08.000000000 -0700
@@ -152,10 +152,18 @@ EXPORT_SYMBOL(unregister_shrinker);
* are eligible for the caller's allocation attempt. It is used for balancing
* slab reclaim versus page reclaim.
*
+ * zone is the zone for which we are shrinking the slabs. If the intent
+ * is to do a global shrink then zone may be NULL. Specification of a
+ * zone is currently only used to limit slab defragmentation to a NUMA node.
+ * The performace of shrink_slab would be better (in particular under NUMA)
+ * if it could be targeted as a whole to the zone that is under memory
+ * pressure but the VFS infrastructure does not allow that at the present
+ * time.
+ *
* Returns the number of slab objects which we shrunk.
*/
unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
- unsigned long lru_pages)
+ unsigned long lru_pages, struct zone *zone)
{
struct shrinker *shrinker;
unsigned long ret = 0;
@@ -218,6 +226,8 @@ unsigned long shrink_slab(unsigned long
shrinker->nr += total_scan;
}
up_read(&shrinker_rwsem);
+ if (gfp_mask & __GFP_FS)
+ kmem_cache_defrag(zone ? zone_to_nid(zone) : -1);
return ret;
}
@@ -1163,7 +1173,8 @@ unsigned long try_to_free_pages(struct z
if (!priority)
disable_swap_token();
nr_reclaimed += shrink_zones(priority, zones, &sc);
- shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
+ shrink_slab(sc.nr_scanned, gfp_mask, lru_pages,
+ NULL);
if (reclaim_state) {
nr_reclaimed += reclaim_state->reclaimed_slab;
reclaim_state->reclaimed_slab = 0;
@@ -1333,7 +1344,7 @@ loop_again:
nr_reclaimed += shrink_zone(priority, zone, &sc);
reclaim_state->reclaimed_slab = 0;
nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
- lru_pages);
+ lru_pages, zone);
nr_reclaimed += reclaim_state->reclaimed_slab;
total_scanned += sc.nr_scanned;
if (zone->all_unreclaimable)
@@ -1601,7 +1612,7 @@ unsigned long shrink_all_memory(unsigned
/* If slab caches are huge, it's better to hit them first */
while (nr_slab >= lru_pages) {
reclaim_state.reclaimed_slab = 0;
- shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
+ shrink_slab(nr_pages, sc.gfp_mask, lru_pages, NULL);
if (!reclaim_state.reclaimed_slab)
break;
@@ -1639,7 +1650,7 @@ unsigned long shrink_all_memory(unsigned
reclaim_state.reclaimed_slab = 0;
shrink_slab(sc.nr_scanned, sc.gfp_mask,
- count_lru_pages());
+ count_lru_pages(), NULL);
ret += reclaim_state.reclaimed_slab;
if (ret >= nr_pages)
goto out;
@@ -1656,7 +1667,8 @@ unsigned long shrink_all_memory(unsigned
if (!ret) {
do {
reclaim_state.reclaimed_slab = 0;
- shrink_slab(nr_pages, sc.gfp_mask, count_lru_pages());
+ shrink_slab(nr_pages, sc.gfp_mask,
+ count_lru_pages(), NULL);
ret += reclaim_state.reclaimed_slab;
} while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
}
@@ -1816,7 +1828,8 @@ static int __zone_reclaim(struct zone *z
* Note that shrink_slab will free memory on all zones and may
* take a long time.
*/
- while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
+ while (shrink_slab(sc.nr_scanned, gfp_mask, order,
+ zone) &&
zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
slab_reclaimable - nr_pages)
;
Index: linux-2.6.22-rc6-mm1/fs/drop_caches.c
===================================================================
--- linux-2.6.22-rc6-mm1.orig/fs/drop_caches.c 2007-07-04 09:53:59.000000000 -0700
+++ linux-2.6.22-rc6-mm1/fs/drop_caches.c 2007-07-04 09:56:22.000000000 -0700
@@ -52,7 +52,7 @@ void drop_slab(void)
int nr_objects;
do {
- nr_objects = shrink_slab(1000, GFP_KERNEL, 1000);
+ nr_objects = shrink_slab(1000, GFP_KERNEL, 1000, NULL);
} while (nr_objects > 10);
}
Index: linux-2.6.22-rc6-mm1/include/linux/mm.h
===================================================================
--- linux-2.6.22-rc6-mm1.orig/include/linux/mm.h 2007-07-04 09:53:59.000000000 -0700
+++ linux-2.6.22-rc6-mm1/include/linux/mm.h 2007-07-04 09:56:22.000000000 -0700
@@ -1248,7 +1248,7 @@ int in_gate_area_no_task(unsigned long a
int drop_caches_sysctl_handler(struct ctl_table *, int, struct file *,
void __user *, size_t *, loff_t *);
unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
- unsigned long lru_pages);
+ unsigned long lru_pages, struct zone *zone);
extern void drop_pagecache_sb(struct super_block *);
void drop_pagecache(void);
void drop_slab(void);
--
-
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