The defrag_ratio is used to set the threshold at which defragmentation should be attempted on a slab page. The allocation ratio is measured by the percentage of the available slots allocated. Add a defrag ratio field and set it to 30% by default. A limit of 30% specified that less than 3 out of 10 available slots for objects are in use before slab defragmeentation runs. Reviewed-by: Rik van Riel Signed-off-by: Christoph Lameter Signed-off-by: Pekka Enberg Signed-off-by: Christoph Lameter --- Documentation/ABI/testing/sysfs-kernel-slab | 13 +++++++++++++ include/linux/slub_def.h | 6 ++++++ mm/slub.c | 23 +++++++++++++++++++++++ 3 files changed, 42 insertions(+) Index: linux-2.6/include/linux/slub_def.h =================================================================== --- linux-2.6.orig/include/linux/slub_def.h 2010-01-29 10:37:01.000000000 -0600 +++ linux-2.6/include/linux/slub_def.h 2010-01-29 10:42:43.000000000 -0600 @@ -91,6 +91,12 @@ struct kmem_cache { int inuse; /* Offset to metadata */ int align; /* Alignment */ unsigned long min_partial; + int defrag_ratio; /* + * Ratio used to check the percentage of + * objects allocate in a slab page. + * If less than this ratio is allocated + * then reclaim attempts are made. + */ const char *name; /* Name (only for display!) */ struct list_head list; /* List of slab caches */ #ifdef CONFIG_SLUB_DEBUG Index: linux-2.6/mm/slub.c =================================================================== --- linux-2.6.orig/mm/slub.c 2010-01-29 10:37:01.000000000 -0600 +++ linux-2.6/mm/slub.c 2010-01-29 10:42:44.000000000 -0600 @@ -2494,6 +2494,7 @@ static int kmem_cache_open(struct kmem_c */ set_min_partial(s, ilog2(s->size)); s->refcount = 1; + s->defrag_ratio = 30; #ifdef CONFIG_NUMA s->remote_node_defrag_ratio = 1000; #endif @@ -4317,6 +4318,27 @@ static ssize_t free_calls_show(struct km } SLAB_ATTR_RO(free_calls); +static ssize_t defrag_ratio_show(struct kmem_cache *s, char *buf) +{ + return sprintf(buf, "%d\n", s->defrag_ratio); +} + +static ssize_t defrag_ratio_store(struct kmem_cache *s, + const char *buf, size_t length) +{ + unsigned long ratio; + int err; + + err = strict_strtoul(buf, 10, &ratio); + if (err) + return err; + + if (ratio < 100) + s->defrag_ratio = ratio; + return length; +} +SLAB_ATTR(defrag_ratio); + #ifdef CONFIG_NUMA static ssize_t remote_node_defrag_ratio_show(struct kmem_cache *s, char *buf) { @@ -4441,6 +4463,7 @@ static struct attribute *slab_attrs[] = &shrink_attr.attr, &alloc_calls_attr.attr, &free_calls_attr.attr, + &defrag_ratio_attr.attr, #ifdef CONFIG_ZONE_DMA &cache_dma_attr.attr, #endif Index: linux-2.6/Documentation/ABI/testing/sysfs-kernel-slab =================================================================== --- linux-2.6.orig/Documentation/ABI/testing/sysfs-kernel-slab 2010-01-29 10:43:21.000000000 -0600 +++ linux-2.6/Documentation/ABI/testing/sysfs-kernel-slab 2010-01-29 10:47:19.000000000 -0600 @@ -180,6 +180,19 @@ Description: list. It can be written to clear the current count. Available when CONFIG_SLUB_STATS is enabled. +What: /sys/kernel/slab/cache/defrag_ratio +Date: February 2010 +KernelVersion: 2.6.34 +Contact: Christoph Lameter + Pekka Enberg , +Description: + The defrag_ratio files allows the control of how agressive + slab fragmentation reduction works at reclaiming objects from + sparsely populated slabs. This is a percentage. If a slab + contains less than this percentage of objects then reclaim + will attempt to reclaim objects so that the whole slab + page can be freed. The default is 30%. + What: /sys/kernel/slab/cache/deactivate_to_tail Date: February 2008 KernelVersion: 2.6.25 -- -- 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/