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Commit 781b2ba6 authored by Pekka Enberg's avatar Pekka Enberg
Browse files

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: default avatarChristoph Lameter <cl@linux-foundation.org>
Acked-by: default avatarMel Gorman <mel@csn.ul.ie>
Tested-by: default avatarLarry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
parent 59a3759d

mm/slub.c

+51 −19
Original line number Diff line number Diff line
@@ -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 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, 
		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)

{