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-rw-r--r--mm/slub.c73
1 files changed, 36 insertions, 37 deletions
diff --git a/mm/slub.c b/mm/slub.c
index f794004813..63d281dfac 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4110,17 +4110,12 @@ static unsigned int slub_min_objects;
* the smallest order which will fit the object.
*/
static inline unsigned int calc_slab_order(unsigned int size,
- unsigned int min_objects, unsigned int max_order,
+ unsigned int min_order, unsigned int max_order,
unsigned int fract_leftover)
{
- unsigned int min_order = slub_min_order;
unsigned int order;
- if (order_objects(min_order, size) > MAX_OBJS_PER_PAGE)
- return get_order(size * MAX_OBJS_PER_PAGE) - 1;
-
- for (order = max(min_order, (unsigned int)get_order(min_objects * size));
- order <= max_order; order++) {
+ for (order = min_order; order <= max_order; order++) {
unsigned int slab_size = (unsigned int)PAGE_SIZE << order;
unsigned int rem;
@@ -4139,16 +4134,8 @@ static inline int calculate_order(unsigned int size)
unsigned int order;
unsigned int min_objects;
unsigned int max_objects;
- unsigned int nr_cpus;
+ unsigned int min_order;
- /*
- * Attempt to find best configuration for a slab. This
- * works by first attempting to generate a layout with
- * the best configuration and backing off gradually.
- *
- * First we increase the acceptable waste in a slab. Then
- * we reduce the minimum objects required in a slab.
- */
min_objects = slub_min_objects;
if (!min_objects) {
/*
@@ -4160,40 +4147,46 @@ static inline int calculate_order(unsigned int size)
* order on systems that appear larger than they are, and too
* low order on systems that appear smaller than they are.
*/
- nr_cpus = num_present_cpus();
+ unsigned int nr_cpus = num_present_cpus();
if (nr_cpus <= 1)
nr_cpus = nr_cpu_ids;
min_objects = 4 * (fls(nr_cpus) + 1);
}
- max_objects = order_objects(slub_max_order, size);
+ /* min_objects can't be 0 because get_order(0) is undefined */
+ max_objects = max(order_objects(slub_max_order, size), 1U);
min_objects = min(min_objects, max_objects);
- while (min_objects > 1) {
- unsigned int fraction;
-
- fraction = 16;
- while (fraction >= 4) {
- order = calc_slab_order(size, min_objects,
- slub_max_order, fraction);
- if (order <= slub_max_order)
- return order;
- fraction /= 2;
- }
- min_objects--;
- }
+ min_order = max_t(unsigned int, slub_min_order,
+ get_order(min_objects * size));
+ if (order_objects(min_order, size) > MAX_OBJS_PER_PAGE)
+ return get_order(size * MAX_OBJS_PER_PAGE) - 1;
/*
- * We were unable to place multiple objects in a slab. Now
- * lets see if we can place a single object there.
+ * Attempt to find best configuration for a slab. This works by first
+ * attempting to generate a layout with the best possible configuration
+ * and backing off gradually.
+ *
+ * We start with accepting at most 1/16 waste and try to find the
+ * smallest order from min_objects-derived/slub_min_order up to
+ * slub_max_order that will satisfy the constraint. Note that increasing
+ * the order can only result in same or less fractional waste, not more.
+ *
+ * If that fails, we increase the acceptable fraction of waste and try
+ * again. The last iteration with fraction of 1/2 would effectively
+ * accept any waste and give us the order determined by min_objects, as
+ * long as at least single object fits within slub_max_order.
*/
- order = calc_slab_order(size, 1, slub_max_order, 1);
- if (order <= slub_max_order)
- return order;
+ for (unsigned int fraction = 16; fraction > 1; fraction /= 2) {
+ order = calc_slab_order(size, min_order, slub_max_order,
+ fraction);
+ if (order <= slub_max_order)
+ return order;
+ }
/*
* Doh this slab cannot be placed using slub_max_order.
*/
- order = calc_slab_order(size, 1, MAX_ORDER, 1);
+ order = get_order(size);
if (order <= MAX_ORDER)
return order;
return -ENOSYS;
@@ -4711,6 +4704,9 @@ static int __init setup_slub_min_order(char *str)
{
get_option(&str, (int *)&slub_min_order);
+ if (slub_min_order > slub_max_order)
+ slub_max_order = slub_min_order;
+
return 1;
}
@@ -4721,6 +4717,9 @@ static int __init setup_slub_max_order(char *str)
get_option(&str, (int *)&slub_max_order);
slub_max_order = min_t(unsigned int, slub_max_order, MAX_ORDER);
+ if (slub_min_order > slub_max_order)
+ slub_min_order = slub_max_order;
+
return 1;
}