mm: SLAB Out-of-memory diagnostics

Following the example at mm/slub.c, add out-of-memory diagnostics to the
SLAB allocator to help on debugging certain OOM conditions.

An example print out looks like this:

  <snip page allocator out-of-memory message>
  SLAB: Unable to allocate memory on node 0 (gfp=0x11200)
    cache: bio-0, object size: 192, order: 0
    node 0: slabs: 3/3, objs: 60/60, free: 0

Signed-off-by: Rafael Aquini <aquini@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

diff --git a/mm/slab.c b/mm/slab.c
index 806a754..67e0e05 100644 (file)
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1731,6 +1731,52 @@ static int __init cpucache_init(void)
 }
 __initcall(cpucache_init);
 
+static noinline void
+slab_out_of_memory(struct kmem_cache *cachep, gfp_t gfpflags, int nodeid)
+{
+       struct kmem_list3 *l3;
+       struct slab *slabp;
+       unsigned long flags;
+       int node;
+
+       printk(KERN_WARNING
+               "SLAB: Unable to allocate memory on node %d (gfp=0x%x)\n",
+               nodeid, gfpflags);
+       printk(KERN_WARNING "  cache: %s, object size: %d, order: %d\n",
+               cachep->name, cachep->buffer_size, cachep->gfporder);
+
+       for_each_online_node(node) {
+               unsigned long active_objs = 0, num_objs = 0, free_objects = 0;
+               unsigned long active_slabs = 0, num_slabs = 0;
+
+               l3 = cachep->nodelists[node];
+               if (!l3)
+                       continue;
+
+               spin_lock_irqsave(&l3->list_lock, flags);
+               list_for_each_entry(slabp, &l3->slabs_full, list) {
+                       active_objs += cachep->num;
+                       active_slabs++;
+               }
+               list_for_each_entry(slabp, &l3->slabs_partial, list) {
+                       active_objs += slabp->inuse;
+                       active_slabs++;
+               }
+               list_for_each_entry(slabp, &l3->slabs_free, list)
+                       num_slabs++;
+
+               free_objects += l3->free_objects;
+               spin_unlock_irqrestore(&l3->list_lock, flags);
+
+               num_slabs += active_slabs;
+               num_objs = num_slabs * cachep->num;
+               printk(KERN_WARNING
+                       "  node %d: slabs: %ld/%ld, objs: %ld/%ld, free: %ld\n",
+                       node, active_slabs, num_slabs, active_objs, num_objs,
+                       free_objects);
+       }
+}
+
 /*
  * Interface to system's page allocator. No need to hold the cache-lock.
  *
@@ -1757,8 +1803,11 @@ static void *kmem_getpages(struct kmem_cache *cachep, gfp_t flags, int nodeid)
                flags |= __GFP_RECLAIMABLE;
 
        page = alloc_pages_exact_node(nodeid, flags | __GFP_NOTRACK, cachep->gfporder);
-       if (!page)
+       if (!page) {
+               if (!(flags & __GFP_NOWARN) && printk_ratelimit())
+                       slab_out_of_memory(cachep, flags, nodeid);
                return NULL;
+       }
 
        nr_pages = (1 << cachep->gfporder);
        if (cachep->flags & SLAB_RECLAIM_ACCOUNT)