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authorEric Dumazet <dada1@cosmosbay.com>2007-05-06 17:49:27 -0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-07 15:12:52 -0400
commit364fbb29a0105863d76a1f7bbc01783a4af30a75 (patch)
tree065828ff023a95daa3b60abbb166e71f10336a64 /mm
parent6ce745ed39d35f9d547d00d406db2be7c6c175b3 (diff)
SLAB: use num_possible_cpus() in enable_cpucache()
The existing comment in mm/slab.c is *perfect*, so I reproduce it : /* * CPU bound tasks (e.g. network routing) can exhibit cpu bound * allocation behaviour: Most allocs on one cpu, most free operations * on another cpu. For these cases, an efficient object passing between * cpus is necessary. This is provided by a shared array. The array * replaces Bonwick's magazine layer. * On uniprocessor, it's functionally equivalent (but less efficient) * to a larger limit. Thus disabled by default. */ As most shiped linux kernels are now compiled with CONFIG_SMP, there is no way a preprocessor #if can detect if the machine is UP or SMP. Better to use num_possible_cpus(). This means on UP we allocate a 'size=0 shared array', to be more efficient. Another patch can later avoid the allocations of 'empty shared arrays', to save some memory. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Acked-by: Pekka Enberg <penberg@cs.helsinki.fi> Acked-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/slab.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/mm/slab.c b/mm/slab.c
index 21b2aef25254..ae440b5ba60e 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4033,10 +4033,8 @@ static int enable_cpucache(struct kmem_cache *cachep)
4033 * to a larger limit. Thus disabled by default. 4033 * to a larger limit. Thus disabled by default.
4034 */ 4034 */
4035 shared = 0; 4035 shared = 0;
4036#ifdef CONFIG_SMP 4036 if (cachep->buffer_size <= PAGE_SIZE && num_possible_cpus() > 1)
4037 if (cachep->buffer_size <= PAGE_SIZE)
4038 shared = 8; 4037 shared = 8;
4039#endif
4040 4038
4041#if DEBUG 4039#if DEBUG
4042 /* 4040 /*