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core: Replace __get_cpu_var with __this_cpu_read if not used for an address.

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__get_cpu_var() can be replaced with this_cpu_read and will then use a
single read instruction with implied address calculation to access the
correct per cpu instance.

However, the address of a per cpu variable passed to __this_cpu_read()
cannot be determined (since it's an implied address conversion through
segment prefixes).  Therefore apply this only to uses of __get_cpu_var
where the address of the variable is not used.

Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Hugh Dickins <hughd@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Christoph Lameter
2010-12-08 16:22:55 +01:00
committed by Tejun Heo
parent 780f36d8b3
commit 909ea96468
13 changed files with 60 additions and 66 deletions
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6
mm/slab.c
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@@ -829,12 +829,12 @@ static void init_reap_node(int cpu)
static void next_reap_node(void)
{
int node = __get_cpu_var(slab_reap_node);
int node = __this_cpu_read(slab_reap_node);
node = next_node(node, node_online_map);
if (unlikely(node >= MAX_NUMNODES))
node = first_node(node_online_map);
__get_cpu_var(slab_reap_node) = node;
__this_cpu_write(slab_reap_node, node);
}
#else
@@ -1012,7 +1012,7 @@ static void __drain_alien_cache(struct kmem_cache *cachep,
*/
static void reap_alien(struct kmem_cache *cachep, struct kmem_list3 *l3)
{
int node = __get_cpu_var(slab_reap_node);
int node = __this_cpu_read(slab_reap_node);
if (l3->alien) {
struct array_cache *ac = l3->alien[node];