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Commit 88a420e4 authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
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slub: add ability to list alloc / free callers per slab 



This patch enables listing the callers who allocated or freed objects in a
cache.

For example to list the allocators for kmalloc-128 do

cat /sys/slab/kmalloc-128/alloc_calls
      7 sn_io_slot_fixup+0x40/0x700
      7 sn_io_slot_fixup+0x80/0x700
      9 sn_bus_fixup+0xe0/0x380
      6 param_sysfs_setup+0xf0/0x280
    276 percpu_populate+0xf0/0x1a0
     19 __register_chrdev_region+0x30/0x360
      8 expand_files+0x2e0/0x6e0
      1 sys_epoll_create+0x60/0x200
      1 __mounts_open+0x140/0x2c0
     65 kmem_alloc+0x110/0x280
      3 alloc_disk_node+0xe0/0x200
     33 as_get_io_context+0x90/0x280
     74 kobject_kset_add_dir+0x40/0x140
     12 pci_create_bus+0x2a0/0x5c0
      1 acpi_ev_create_gpe_block+0x120/0x9e0
     41 con_insert_unipair+0x100/0x1c0
      1 uart_open+0x1c0/0xba0
      1 dma_pool_create+0xe0/0x340
      2 neigh_table_init_no_netlink+0x260/0x4c0
      6 neigh_parms_alloc+0x30/0x200
      1 netlink_kernel_create+0x130/0x320
      5 fz_hash_alloc+0x50/0xe0
      2 sn_common_hubdev_init+0xd0/0x6e0
     28 kernel_param_sysfs_setup+0x30/0x180
     72 process_zones+0x70/0x2e0

cat /sys/slab/kmalloc-128/free_calls
    558 <not-available>
      3 sn_io_slot_fixup+0x600/0x700
     84 free_fdtable_rcu+0x120/0x260
      2 seq_release+0x40/0x60
      6 kmem_free+0x70/0xc0
     24 free_as_io_context+0x20/0x200
      1 acpi_get_object_info+0x3a0/0x3e0
      1 acpi_add_single_object+0xcf0/0x1e40
      2 con_release_unimap+0x80/0x140
      1 free+0x20/0x40

SLAB_STORE_USER must be enabled for a slab cache by either booting with
"slab_debug" or enabling user tracking specifically for the slab of interest.

Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e95eed57

mm/slub.c

+181 −3
Original line number Diff line number Diff line
@@ -97,9 +97,6 @@ 
 *

 * - Support PAGE_ALLOC_DEBUG. Should be easy to do.

 *

 * - Support DEBUG_SLAB_LEAK. Trouble is we do not know where the full

 *   slabs are in SLUB.

 *

 * - SLAB_DEBUG_INITIAL is not supported but I have never seen a use of

 *   it.

 *
@@ -2659,6 +2656,169 @@ static unsigned long validate_slab_cache(struct kmem_cache *s) 
	return count;

}



/*

 * Generate lists of locations where slabcache objects are allocated

 * and freed.

 */



struct location {

	unsigned long count;

	void *addr;

};



struct loc_track {

	unsigned long max;

	unsigned long count;

	struct location *loc;

};



static void free_loc_track(struct loc_track *t)

{

	if (t->max)

		free_pages((unsigned long)t->loc,

			get_order(sizeof(struct location) * t->max));

}



static int alloc_loc_track(struct loc_track *t, unsigned long max)

{

	struct location *l;

	int order;



	if (!max)

		max = PAGE_SIZE / sizeof(struct location);



	order = get_order(sizeof(struct location) * max);



	l = (void *)__get_free_pages(GFP_KERNEL, order);



	if (!l)

		return 0;



	if (t->count) {

		memcpy(l, t->loc, sizeof(struct location) * t->count);

		free_loc_track(t);

	}

	t->max = max;

	t->loc = l;

	return 1;

}



static int add_location(struct loc_track *t, struct kmem_cache *s,

						void *addr)

{

	long start, end, pos;

	struct location *l;

	void *caddr;



	start = -1;

	end = t->count;



	for ( ; ; ) {

		pos = start + (end - start + 1) / 2;



		/*

		 * There is nothing at "end". If we end up there

		 * we need to add something to before end.

		 */

		if (pos == end)

			break;



		caddr = t->loc[pos].addr;

		if (addr == caddr) {

			t->loc[pos].count++;

			return 1;

		}



		if (addr < caddr)

			end = pos;

		else

			start = pos;

	}



	/*

	 * Not found. Insert new tracking element

	 */

	if (t->count >= t->max && !alloc_loc_track(t, 2 * t->max))

		return 0;



	l = t->loc + pos;

	if (pos < t->count)

		memmove(l + 1, l,

			(t->count - pos) * sizeof(struct location));

	t->count++;

	l->count = 1;

	l->addr = addr;

	return 1;

}



static void process_slab(struct loc_track *t, struct kmem_cache *s,

		struct page *page, enum track_item alloc)

{

	void *addr = page_address(page);

	unsigned long map[BITS_TO_LONGS(s->objects)];

	void *p;



	bitmap_zero(map, s->objects);

	for (p = page->freelist; p; p = get_freepointer(s, p))

		set_bit((p - addr) / s->size, map);



	for (p = addr; p < addr + s->objects * s->size; p += s->size)

		if (!test_bit((p - addr) / s->size, map)) {

			void *addr = get_track(s, p, alloc)->addr;



			add_location(t, s, addr);

		}

}



static int list_locations(struct kmem_cache *s, char *buf,

					enum track_item alloc)

{

	int n = 0;

	unsigned long i;

	struct loc_track t;

	int node;



	t.count = 0;

	t.max = 0;



	/* Push back cpu slabs */

	flush_all(s);



	for_each_online_node(node) {

		struct kmem_cache_node *n = get_node(s, node);

		unsigned long flags;

		struct page *page;



		if (!atomic_read(&n->nr_slabs))

			continue;



		spin_lock_irqsave(&n->list_lock, flags);

		list_for_each_entry(page, &n->partial, lru)

			process_slab(&t, s, page, alloc);

		list_for_each_entry(page, &n->full, lru)

			process_slab(&t, s, page, alloc);

		spin_unlock_irqrestore(&n->list_lock, flags);

	}



	for (i = 0; i < t.count; i++) {

		void *addr = t.loc[i].addr;



		if (n > PAGE_SIZE - 100)

			break;

		n += sprintf(buf + n, "%7ld ", t.loc[i].count);

		if (addr)

			n += sprint_symbol(buf + n, (unsigned long)t.loc[i].addr);

		else

			n += sprintf(buf + n, "<not-available>");

		n += sprintf(buf + n, "\n");

	}



	free_loc_track(&t);

	if (!t.count)

		n += sprintf(buf, "No data\n");

	return n;

}



static unsigned long count_partial(struct kmem_cache_node *n)

{

	unsigned long flags;
@@ -3009,6 +3169,22 @@ static ssize_t validate_store(struct kmem_cache *s, 
}

SLAB_ATTR(validate);



static ssize_t alloc_calls_show(struct kmem_cache *s, char *buf)

{

	if (!(s->flags & SLAB_STORE_USER))

		return -ENOSYS;

	return list_locations(s, buf, TRACK_ALLOC);

}

SLAB_ATTR_RO(alloc_calls);



static ssize_t free_calls_show(struct kmem_cache *s, char *buf)

{

	if (!(s->flags & SLAB_STORE_USER))

		return -ENOSYS;

	return list_locations(s, buf, TRACK_FREE);

}

SLAB_ATTR_RO(free_calls);



#ifdef CONFIG_NUMA

static ssize_t defrag_ratio_show(struct kmem_cache *s, char *buf)

{
@@ -3049,6 +3225,8 @@ static struct attribute * slab_attrs[] = { 
	&poison_attr.attr,

	&store_user_attr.attr,

	&validate_attr.attr,

	&alloc_calls_attr.attr,

	&free_calls_attr.attr,

#ifdef CONFIG_ZONE_DMA

	&cache_dma_attr.attr,

#endif