SLUB: Out-of-memory diagnostics

As suggested by Mel Gorman, add out-of-memory diagnostics to the SLUB allocator
to make debugging OOM conditions easier. This patch helped hunt down a nasty
OOM issue that popped up every now that was caused by SLUB debugging code which
forced 4096 byte allocations to use order 1 pages even in the fallback case.

An example print out looks like this:

  <snip page allocator out-of-memory message>
  SLUB: Unable to allocate memory on node -1 (gfp=20)
    cache: kmalloc-4096, object size: 4096, buffer size: 4168, default order: 3, min order: 1
    node 0: slabs: 95, objs: 665, free: 0

Acked-by: Christoph Lameter <cl@linux-foundation.org>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

1 files changed, 51 insertions, 19 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 65ffda5934b..a5a4ecf7e39 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1484,6 +1484,56 @@ static inline int node_match(struct kmem_cache_cpu *c, int node)
         return 1;
 }
 
+static int count_free(struct page *page)
+{
+        return page->objects - page->inuse;
+}
+
+static unsigned long count_partial(struct kmem_cache_node *n,
+                                        int (*get_count)(struct page *))
+{
+        unsigned long flags;
+        unsigned long x = 0;
+        struct page *page;
+
+        spin_lock_irqsave(&n->list_lock, flags);
+        list_for_each_entry(page, &n->partial, lru)
+                x += get_count(page);
+        spin_unlock_irqrestore(&n->list_lock, flags);
+        return x;
+}
+
+static noinline void
+slab_out_of_memory(struct kmem_cache *s, gfp_t gfpflags, int nid)
+{
+        int node;
+
+        printk(KERN_WARNING
+                "SLUB: Unable to allocate memory on node %d (gfp=0x%x)\n",
+                nid, gfpflags);
+        printk(KERN_WARNING "  cache: %s, object size: %d, buffer size: %d, "
+                "default order: %d, min order: %d\n", s->name, s->objsize,
+                s->size, oo_order(s->oo), oo_order(s->min));
+
+        for_each_online_node(node) {
+                struct kmem_cache_node *n = get_node(s, node);
+                unsigned long nr_slabs;
+                unsigned long nr_objs;
+                unsigned long nr_free;
+
+                if (!n)
+                        continue;
+
+                nr_slabs = atomic_long_read(&n->nr_slabs);
+                nr_objs = atomic_long_read(&n->total_objects);
+                nr_free = count_partial(n, count_free);
+
+                printk(KERN_WARNING
+                        "  node %d: slabs: %ld, objs: %ld, free: %ld\n",
+                        node, nr_slabs, nr_objs, nr_free);
+        }
+}
+
 /*
  * Slow path. The lockless freelist is empty or we need to perform
  * debugging duties.
@@ -1565,6 +1615,7 @@ new_slab:
                 c->page = new;
                 goto load_freelist;
         }
+        slab_out_of_memory(s, gfpflags, node);
         return NULL;
 debug:
         if (!alloc_debug_processing(s, c->page, object, addr))
@@ -3318,20 +3369,6 @@ void *__kmalloc_node_track_caller(size_t size, gfp_t gfpflags,
 }
 
 #ifdef CONFIG_SLUB_DEBUG
-static unsigned long count_partial(struct kmem_cache_node *n,
-                                        int (*get_count)(struct page *))
-{
-        unsigned long flags;
-        unsigned long x = 0;
-        struct page *page;
-
-        spin_lock_irqsave(&n->list_lock, flags);
-        list_for_each_entry(page, &n->partial, lru)
-                x += get_count(page);
-        spin_unlock_irqrestore(&n->list_lock, flags);
-        return x;
-}
-
 static int count_inuse(struct page *page)
 {
         return page->inuse;
@@ -3342,11 +3379,6 @@ static int count_total(struct page *page)
         return page->objects;
 }
 
-static int count_free(struct page *page)
-{
-        return page->objects - page->inuse;
-}
-
 static int validate_slab(struct kmem_cache *s, struct page *page,
                                                 unsigned long *map)
 {