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| author | Eric Dumazet <dada1@cosmosbay.com> | 2007-05-06 23:49:27 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-05-07 21:12:52 +0200 |
| commit | 364fbb29a0105863d76a1f7bbc01783a4af30a75 (patch) | |
| tree | 065828ff023a95daa3b60abbb166e71f10336a64 /mm/slab.c | |
| parent | readahead: code cleanup (diff) | |
| download | linux-364fbb29a0105863d76a1f7bbc01783a4af30a75.tar.xz linux-364fbb29a0105863d76a1f7bbc01783a4af30a75.zip | |
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/slab.c')
| -rw-r--r-- | mm/slab.c | 4 |
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) * to a larger limit. Thus disabled by default. */ shared = 0; -#ifdef CONFIG_SMP - if (cachep->buffer_size <= PAGE_SIZE) + if (cachep->buffer_size <= PAGE_SIZE && num_possible_cpus() > 1) shared = 8; -#endif #if DEBUG /* |