On a large SMP systems with hundreds of CPUs, the current thresholds
for allocating and freeing debug objects (256 and 1024 respectively)
may not work well. This can cause a lot of needless calls to
kmem_aloc() and kmem_free() on those systems.

To alleviate this thrashing problem, the object freeing threshold
is now increased to "1024 + # of CPUs * 32". Whereas the object
allocation threshold is increased to "256 + # of CPUs * 4". That
should make the debug objects subsystem scale better with the number
of CPUs available in the system.

Signed-off-by: Waiman Long <long...@redhat.com>
---
 lib/debugobjects.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index a8e1260..bb415a7 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -52,7 +52,10 @@ struct debug_bucket {
 static int                     debug_objects_warnings __read_mostly;
 static int                     debug_objects_enabled __read_mostly
                                = CONFIG_DEBUG_OBJECTS_ENABLE_DEFAULT;
-
+static int                     debug_objects_pool_size __read_mostly
+                               = ODEBUG_POOL_SIZE;
+static int                     debug_objects_pool_min_level __read_mostly
+                               = ODEBUG_POOL_MIN_LEVEL;
 static struct debug_obj_descr  *descr_test  __read_mostly;
 
 static void free_obj_work(struct work_struct *work);
@@ -88,13 +91,13 @@ static void fill_pool(void)
        struct debug_obj *new;
        unsigned long flags;
 
-       if (likely(obj_pool_free >= ODEBUG_POOL_MIN_LEVEL))
+       if (likely(obj_pool_free >= debug_objects_pool_min_level))
                return;
 
        if (unlikely(!obj_cache))
                return;
 
-       while (obj_pool_free < ODEBUG_POOL_MIN_LEVEL) {
+       while (obj_pool_free < debug_objects_pool_min_level) {
 
                new = kmem_cache_zalloc(obj_cache, gfp);
                if (!new)
@@ -169,7 +172,7 @@ static void free_obj_work(struct work_struct *work)
        unsigned long flags;
 
        raw_spin_lock_irqsave(&pool_lock, flags);
-       while (obj_pool_free > ODEBUG_POOL_SIZE) {
+       while (obj_pool_free > debug_objects_pool_size) {
                obj = hlist_entry(obj_pool.first, typeof(*obj), node);
                hlist_del(&obj->node);
                obj_pool_free--;
@@ -198,7 +201,7 @@ static void free_object(struct debug_obj *obj)
         * schedule work when the pool is filled and the cache is
         * initialized:
         */
-       if (obj_pool_free > ODEBUG_POOL_SIZE && obj_cache)
+       if (obj_pool_free > debug_objects_pool_size && obj_cache)
                sched = keventd_up();
        hlist_add_head(&obj->node, &obj_pool);
        obj_pool_free++;
@@ -1108,4 +1111,11 @@ void __init debug_objects_mem_init(void)
                pr_warn("out of memory.\n");
        } else
                debug_objects_selftest();
+
+       /*
+        * Increase the thresholds for allocating and freeing objects
+        * according to the number of possible CPUs available in the system.
+        */
+       debug_objects_pool_size += num_possible_cpus() * 32;
+       debug_objects_pool_min_level += num_possible_cpus() * 4;
 }
-- 
1.8.3.1

Reply via email to