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 --- 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); -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/