Using cpu alloc removes the needs for the per cpu arrays in the kmem_cache struct.
These could get quite big if we have to support system of up to thousands of cpus.
The use of cpu_alloc means that:
1. The size of kmem_cache for SMP configuration shrinks since we will only
need 1 pointer instead of NR_CPUS. The same pointer can be used by all
processors. Reduces cache footprint of the allocator.
2. We can dynamically size kmem_cache according to the actual nodes in the
system meaning less memory overhead for configurations that may potentially
support up to 1k NUMA nodes / 4k cpus.
3. We can remove the diddle widdle with allocating and releasing of
kmem_cache_cpu structures when bringing up and shutting down cpus. The cpu
alloc logic will do it all for us. Removes some portions of the cpu hotplug
functionality.
4. Fastpath performance increases.
Signed-off-by: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
Index: linux-2.6/include/linux/slub_def.h
===================================================================
--- linux-2.6.orig/include/linux/slub_def.h 2008-10-03 09:05:11.000000000 -0500
+++ linux-2.6/include/linux/slub_def.h 2008-10-03 10:17:32.000000000 -0500
@@ -68,6 +68,7 @@
* Slab cache management.
*/
struct kmem_cache {
+ struct kmem_cache_cpu *cpu_slab;
/* Used for retriving partial slabs etc */
unsigned long flags;
int size; /* The size of an object including meta data */
@@ -102,11 +103,6 @@
int remote_node_defrag_ratio;
struct kmem_cache_node *node[MAX_NUMNODES];
#endif
-#ifdef CONFIG_SMP
- struct kmem_cache_cpu *cpu_slab[NR_CPUS];
-#else
- struct kmem_cache_cpu cpu_slab;
-#endif
};