mm, slab: suppress out of memory warning unless debug is enabled

When the slab or slub allocators cannot allocate additional slab pages,
they emit diagnostic information to the kernel log such as current
number of slabs, number of objects, active objects, etc.  This is always
coupled with a page allocation failure warning since it is controlled by
!__GFP_NOWARN.

Suppress this out of memory warning if the allocator is configured
without debug supported.  The page allocation failure warning will
indicate it is a failed slab allocation, the order, and the gfp mask, so
this is only useful to diagnose allocator issues.

Since CONFIG_SLUB_DEBUG is already enabled by default for the slub
allocator, there is no functional change with this patch.  If debug is
disabled, however, the warnings are now suppressed.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slab.c

@@ -1621,10 +1621,16 @@ __initcall(cpucache_init);
 static noinline void
 slab_out_of_memory(struct kmem_cache *cachep, gfp_t gfpflags, int nodeid)
 {
+#if DEBUG
 	struct kmem_cache_node *n;
 	struct page *page;
 	unsigned long flags;
 	int node;
+	static DEFINE_RATELIMIT_STATE(slab_oom_rs, DEFAULT_RATELIMIT_INTERVAL,
+				      DEFAULT_RATELIMIT_BURST);
+
+	if ((gfpflags & __GFP_NOWARN) || !__ratelimit(&slab_oom_rs))
+		return;
 
 	printk(KERN_WARNING
 		"SLAB: Unable to allocate memory on node %d (gfp=0x%x)\n",
@@ -1662,6 +1668,7 @@ slab_out_of_memory(struct kmem_cache *cachep, gfp_t gfpflags, int nodeid)
 			node, active_slabs, num_slabs, active_objs, num_objs,
 			free_objects);
 	}
+#endif
 }
 
 /*
@@ -1683,8 +1690,7 @@ static struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
 
 	page = alloc_pages_exact_node(nodeid, flags | __GFP_NOTRACK, cachep->gfporder);
 	if (!page) {
-		if (!(flags & __GFP_NOWARN) && printk_ratelimit())
-			slab_out_of_memory(cachep, flags, nodeid);
+		slab_out_of_memory(cachep, flags, nodeid);
 		return NULL;
 	}
 

mm/slub.c

@@ -2119,11 +2119,19 @@ static inline int node_match(struct page *page, int node)
 	return 1;
 }
 
+#ifdef CONFIG_SLUB_DEBUG
 static int count_free(struct page *page)
 {
 	return page->objects - page->inuse;
 }
 
+static inline unsigned long node_nr_objs(struct kmem_cache_node *n)
+{
+	return atomic_long_read(&n->total_objects);
+}
+#endif /* CONFIG_SLUB_DEBUG */
+
+#if defined(CONFIG_SLUB_DEBUG) || defined(CONFIG_SYSFS)
 static unsigned long count_partial(struct kmem_cache_node *n,
 					int (*get_count)(struct page *))
 {
@@ -2137,21 +2145,19 @@ static unsigned long count_partial(struct kmem_cache_node *n,
 	spin_unlock_irqrestore(&n->list_lock, flags);
 	return x;
 }
-
-static inline unsigned long node_nr_objs(struct kmem_cache_node *n)
-{
-#ifdef CONFIG_SLUB_DEBUG
-	return atomic_long_read(&n->total_objects);
-#else
-	return 0;
-#endif
-}
+#endif /* CONFIG_SLUB_DEBUG || CONFIG_SYSFS */
 
 static noinline void
 slab_out_of_memory(struct kmem_cache *s, gfp_t gfpflags, int nid)
 {
+#ifdef CONFIG_SLUB_DEBUG
+	static DEFINE_RATELIMIT_STATE(slub_oom_rs, DEFAULT_RATELIMIT_INTERVAL,
+				      DEFAULT_RATELIMIT_BURST);
 	int node;
 
+	if ((gfpflags & __GFP_NOWARN) || !__ratelimit(&slub_oom_rs))
+		return;
+
 	pr_warn("SLUB: Unable to allocate memory on node %d (gfp=0x%x)\n",
 		nid, gfpflags);
 	pr_warn("  cache: %s, object size: %d, buffer size: %d, default order: %d, min order: %d\n",
@@ -2178,6 +2184,7 @@ slab_out_of_memory(struct kmem_cache *s, gfp_t gfpflags, int nid)
 		pr_warn("  node %d: slabs: %ld, objs: %ld, free: %ld\n",
 			node, nr_slabs, nr_objs, nr_free);
 	}
+#endif
 }
 
 static inline void *new_slab_objects(struct kmem_cache *s, gfp_t flags,
@@ -2356,9 +2363,7 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 	freelist = new_slab_objects(s, gfpflags, node, &c);
 
 	if (unlikely(!freelist)) {
-		if (!(gfpflags & __GFP_NOWARN) && printk_ratelimit())
-			slab_out_of_memory(s, gfpflags, node);
-
+		slab_out_of_memory(s, gfpflags, node);
 		local_irq_restore(flags);
 		return NULL;
 	}