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SLUB: dynamic per-cache MIN_PARTIAL

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This patch changes the static MIN_PARTIAL to a dynamic per-cache ->min_partial
value that is calculated from object size. The bigger the object size, the more
pages we keep on the partial list.

I tested SLAB, SLUB, and SLUB with this patch on Jens Axboe's 'netio' example
script of the fio benchmarking tool. The script stresses the networking
subsystem which should also give a fairly good beating of kmalloc() et al.

To run the test yourself, first clone the fio repository:

  git clone git://git.kernel.dk/fio.git

and then run the following command n times on your machine:

  time ./fio examples/netio

The results on my 2-way 64-bit x86 machine are as follows:

  [ the minimum, maximum, and average are captured from 50 individual runs ]

                 real time (seconds)
                 min      max      avg      sd
  SLAB           22.76    23.38    22.98    0.17
  SLUB           22.80    25.78    23.46    0.72
  SLUB (dynamic) 22.74    23.54    23.00    0.20

                 sys time (seconds)
                 min      max      avg      sd
  SLAB           6.90     8.28     7.70     0.28
  SLUB           7.42     16.95    8.89     2.28
  SLUB (dynamic) 7.17     8.64     7.73     0.29

                 user time (seconds)
                 min      max      avg      sd
  SLAB           36.89    38.11    37.50    0.29
  SLUB           30.85    37.99    37.06    1.67
  SLUB (dynamic) 36.75    38.07    37.59    0.32

As you can see from the above numbers, this patch brings SLUB to the same level
as SLAB for this particular workload fixing a ~2% regression. I'd expect this
change to help similar workloads that allocate a lot of objects that are close
to the size of a page.

Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
This commit is contained in:
Pekka Enberg 2008-08-05 09:28:47 +03:00
parent 231367fd9b
commit 5595cffc82
2 changed files with 20 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

1
include/linux/slub_def.h
View file

@ -46,6 +46,7 @@ struct kmem_cache_cpu {
struct kmem_cache_node {
spinlock_t list_lock; /* Protect partial list and nr_partial */
unsigned long nr_partial;
unsigned long min_partial;
struct list_head partial;
#ifdef CONFIG_SLUB_DEBUG
atomic_long_t nr_slabs;

26
mm/slub.c
View file

@ -1329,7 +1329,7 @@ static struct page *get_any_partial(struct kmem_cache *s, gfp_t flags)
n = get_node(s, zone_to_nid(zone));
if (n && cpuset_zone_allowed_hardwall(zone, flags) &&
n->nr_partial > MIN_PARTIAL) {
n->nr_partial > n->min_partial) {
page = get_partial_node(n);
if (page)
return page;
@ -1381,7 +1381,7 @@ static void unfreeze_slab(struct kmem_cache *s, struct page *page, int tail)
slab_unlock(page);
} else {
stat(c, DEACTIVATE_EMPTY);
if (n->nr_partial < MIN_PARTIAL) {
if (n->nr_partial < n->min_partial) {
/*
* Adding an empty slab to the partial slabs in order
* to avoid page allocator overhead. This slab needs
@ -1913,9 +1913,21 @@ static void init_kmem_cache_cpu(struct kmem_cache *s,
#endif
}
static void init_kmem_cache_node(struct kmem_cache_node *n)
static void
init_kmem_cache_node(struct kmem_cache_node *n, struct kmem_cache *s)
{
n->nr_partial = 0;
/*
* The larger the object size is, the more pages we want on the partial
* list to avoid pounding the page allocator excessively.
*/
n->min_partial = ilog2(s->size);
if (n->min_partial < MIN_PARTIAL)
n->min_partial = MIN_PARTIAL;
else if (n->min_partial > MAX_PARTIAL)
n->min_partial = MAX_PARTIAL;
spin_lock_init(&n->list_lock);
INIT_LIST_HEAD(&n->partial);
#ifdef CONFIG_SLUB_DEBUG
@ -2087,7 +2099,7 @@ static struct kmem_cache_node *early_kmem_cache_node_alloc(gfp_t gfpflags,
init_object(kmalloc_caches, n, 1);
init_tracking(kmalloc_caches, n);
#endif
init_kmem_cache_node(n);
init_kmem_cache_node(n, kmalloc_caches);
inc_slabs_node(kmalloc_caches, node, page->objects);
/*
@ -2144,7 +2156,7 @@ static int init_kmem_cache_nodes(struct kmem_cache *s, gfp_t gfpflags)
}
s->node[node] = n;
init_kmem_cache_node(n);
init_kmem_cache_node(n, s);
}
return 1;
}
@ -2155,7 +2167,7 @@ static void free_kmem_cache_nodes(struct kmem_cache *s)
static int init_kmem_cache_nodes(struct kmem_cache *s, gfp_t gfpflags)
{
init_kmem_cache_node(&s->local_node);
init_kmem_cache_node(&s->local_node, s);
return 1;
}
#endif
@ -2889,7 +2901,7 @@ static int slab_mem_going_online_callback(void *arg)
ret = -ENOMEM;
goto out;
}
init_kmem_cache_node(n);
init_kmem_cache_node(n, s);
s->node[nid] = n;
}
out: