SLUB: Fix default slab order for big object sizes
The default order of kmalloc-8192 on 2*4 stoakley is an issue of
calculate_order.
slab_size order name
-------------------------------------------------
4096 3 sgpool-128
8192 2 kmalloc-8192
16384 3 kmalloc-16384
kmalloc-8192's default order is smaller than sgpool-128's.
On 4*4 tigerton machine, a similiar issue appears on another kmem_cache.
Function calculate_order uses 'min_objects /= 2;' to shrink. Plus size
calculation/checking in slab_order, sometimes above issue appear.
Below patch against 2.6.29-rc2 fixes it.
I checked the default orders of all kmem_cache and they don't become
smaller than before. So the patch wouldn't hurt performance.
Signed-off-by Zhang Yanmin <yanmin.zhang@linux.intel.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
diff --git a/mm/slub.c b/mm/slub.c
index 5a5e7f5..c01a7a3 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1844,6 +1844,7 @@
int order;
int min_objects;
int fraction;
+ int max_objects;
/*
* Attempt to find best configuration for a slab. This
@@ -1856,6 +1857,9 @@
min_objects = slub_min_objects;
if (!min_objects)
min_objects = 4 * (fls(nr_cpu_ids) + 1);
+ max_objects = (PAGE_SIZE << slub_max_order)/size;
+ min_objects = min(min_objects, max_objects);
+
while (min_objects > 1) {
fraction = 16;
while (fraction >= 4) {
@@ -1865,7 +1869,7 @@
return order;
fraction /= 2;
}
- min_objects /= 2;
+ min_objects --;
}
/*