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slub: Dynamically size kmalloc cache allocations
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kmalloc caches are statically defined and may take up a lot of space just
because the sizes of the node array has to be dimensioned for the largest
node count supported.

This patch makes the size of the kmem_cache structure dynamic throughout by
creating a kmem_cache slab cache for the kmem_cache objects. The bootstrap
occurs by allocating the initial one or two kmem_cache objects from the
page allocator.

C2->C3
	- Fix various issues indicated by David
	- Make create kmalloc_cache return a kmem_cache * pointer.

Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
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Christoph Lameter authored and Pekka Enberg committed Oct 2, 2010
1 parent 6c182dc commit 51df114
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Showing 2 changed files with 140 additions and 58 deletions.
7 changes: 2 additions & 5 deletions include/linux/slub_def.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -139,19 +139,16 @@ struct kmem_cache {

#ifdef CONFIG_ZONE_DMA
#define SLUB_DMA __GFP_DMA
/* Reserve extra caches for potential DMA use */
#define KMALLOC_CACHES (2 * SLUB_PAGE_SHIFT)
#else
/* Disable DMA functionality */
#define SLUB_DMA (__force gfp_t)0
#define KMALLOC_CACHES SLUB_PAGE_SHIFT
#endif

/*
* We keep the general caches in an array of slab caches that are used for
* 2^x bytes of allocations.
*/
extern struct kmem_cache kmalloc_caches[KMALLOC_CACHES];
extern struct kmem_cache *kmalloc_caches[SLUB_PAGE_SHIFT];

/*
* Sorry that the following has to be that ugly but some versions of GCC
Expand Down Expand Up @@ -216,7 +213,7 @@ static __always_inline struct kmem_cache *kmalloc_slab(size_t size)
if (index == 0)
return NULL;

return &kmalloc_caches[index];
return kmalloc_caches[index];
}

void *kmem_cache_alloc(struct kmem_cache *, gfp_t);
Expand Down
191 changes: 138 additions & 53 deletions mm/slub.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -168,7 +168,6 @@ static inline int kmem_cache_debug(struct kmem_cache *s)

/* Internal SLUB flags */
#define __OBJECT_POISON 0x80000000UL /* Poison object */
#define __SYSFS_ADD_DEFERRED 0x40000000UL /* Not yet visible via sysfs */

static int kmem_size = sizeof(struct kmem_cache);

Expand All @@ -178,7 +177,7 @@ static struct notifier_block slab_notifier;

static enum {
DOWN, /* No slab functionality available */
PARTIAL, /* kmem_cache_open() works but kmalloc does not */
PARTIAL, /* Kmem_cache_node works */
UP, /* Everything works but does not show up in sysfs */
SYSFS /* Sysfs up */
} slab_state = DOWN;
Expand Down Expand Up @@ -2073,6 +2072,8 @@ static inline int alloc_kmem_cache_cpus(struct kmem_cache *s)
}

#ifdef CONFIG_NUMA
static struct kmem_cache *kmem_cache_node;

/*
* No kmalloc_node yet so do it by hand. We know that this is the first
* slab on the node for this slabcache. There are no concurrent accesses
Expand All @@ -2088,9 +2089,9 @@ static void early_kmem_cache_node_alloc(int node)
struct kmem_cache_node *n;
unsigned long flags;

BUG_ON(kmalloc_caches->size < sizeof(struct kmem_cache_node));
BUG_ON(kmem_cache_node->size < sizeof(struct kmem_cache_node));

page = new_slab(kmalloc_caches, GFP_NOWAIT, node);
page = new_slab(kmem_cache_node, GFP_NOWAIT, node);

BUG_ON(!page);
if (page_to_nid(page) != node) {
Expand All @@ -2102,15 +2103,15 @@ static void early_kmem_cache_node_alloc(int node)

n = page->freelist;
BUG_ON(!n);
page->freelist = get_freepointer(kmalloc_caches, n);
page->freelist = get_freepointer(kmem_cache_node, n);
page->inuse++;
kmalloc_caches->node[node] = n;
kmem_cache_node->node[node] = n;
#ifdef CONFIG_SLUB_DEBUG
init_object(kmalloc_caches, n, 1);
init_tracking(kmalloc_caches, n);
init_object(kmem_cache_node, n, 1);
init_tracking(kmem_cache_node, n);
#endif
init_kmem_cache_node(n, kmalloc_caches);
inc_slabs_node(kmalloc_caches, node, page->objects);
init_kmem_cache_node(n, kmem_cache_node);
inc_slabs_node(kmem_cache_node, node, page->objects);

/*
* lockdep requires consistent irq usage for each lock
Expand All @@ -2128,8 +2129,10 @@ static void free_kmem_cache_nodes(struct kmem_cache *s)

for_each_node_state(node, N_NORMAL_MEMORY) {
struct kmem_cache_node *n = s->node[node];

if (n)
kmem_cache_free(kmalloc_caches, n);
kmem_cache_free(kmem_cache_node, n);

s->node[node] = NULL;
}
}
Expand All @@ -2145,7 +2148,7 @@ static int init_kmem_cache_nodes(struct kmem_cache *s)
early_kmem_cache_node_alloc(node);
continue;
}
n = kmem_cache_alloc_node(kmalloc_caches,
n = kmem_cache_alloc_node(kmem_cache_node,
GFP_KERNEL, node);

if (!n) {
Expand Down Expand Up @@ -2498,11 +2501,13 @@ EXPORT_SYMBOL(kmem_cache_destroy);
* Kmalloc subsystem
*******************************************************************/

struct kmem_cache kmalloc_caches[KMALLOC_CACHES] __cacheline_aligned;
struct kmem_cache *kmalloc_caches[SLUB_PAGE_SHIFT];
EXPORT_SYMBOL(kmalloc_caches);

static struct kmem_cache *kmem_cache;

#ifdef CONFIG_ZONE_DMA
static struct kmem_cache kmalloc_dma_caches[SLUB_PAGE_SHIFT];
static struct kmem_cache *kmalloc_dma_caches[SLUB_PAGE_SHIFT];
#endif

static int __init setup_slub_min_order(char *str)
Expand Down Expand Up @@ -2541,9 +2546,13 @@ static int __init setup_slub_nomerge(char *str)

__setup("slub_nomerge", setup_slub_nomerge);

static void create_kmalloc_cache(struct kmem_cache *s,
const char *name, int size, unsigned int flags)
static struct kmem_cache *__init create_kmalloc_cache(const char *name,
int size, unsigned int flags)
{
struct kmem_cache *s;

s = kmem_cache_alloc(kmem_cache, GFP_NOWAIT);

/*
* This function is called with IRQs disabled during early-boot on
* single CPU so there's no need to take slub_lock here.
Expand All @@ -2553,12 +2562,11 @@ static void create_kmalloc_cache(struct kmem_cache *s,
goto panic;

list_add(&s->list, &slab_caches);

if (!sysfs_slab_add(s))
return;
return s;

panic:
panic("Creation of kmalloc slab %s size=%d failed.\n", name, size);
return NULL;
}

/*
Expand Down Expand Up @@ -2613,10 +2621,10 @@ static struct kmem_cache *get_slab(size_t size, gfp_t flags)

#ifdef CONFIG_ZONE_DMA
if (unlikely((flags & SLUB_DMA)))
return &kmalloc_dma_caches[index];
return kmalloc_dma_caches[index];

#endif
return &kmalloc_caches[index];
return kmalloc_caches[index];
}

void *__kmalloc(size_t size, gfp_t flags)
Expand Down Expand Up @@ -2940,46 +2948,113 @@ static int slab_memory_callback(struct notifier_block *self,
* Basic setup of slabs
*******************************************************************/

/*
* Used for early kmem_cache structures that were allocated using
* the page allocator
*/

static void __init kmem_cache_bootstrap_fixup(struct kmem_cache *s)
{
int node;

list_add(&s->list, &slab_caches);
s->refcount = -1;

for_each_node_state(node, N_NORMAL_MEMORY) {
struct kmem_cache_node *n = get_node(s, node);
struct page *p;

if (n) {
list_for_each_entry(p, &n->partial, lru)
p->slab = s;

#ifdef CONFIG_SLAB_DEBUG
list_for_each_entry(p, &n->full, lru)
p->slab = s;
#endif
}
}
}

void __init kmem_cache_init(void)
{
int i;
int caches = 0;
struct kmem_cache *temp_kmem_cache;
int order;

#ifdef CONFIG_NUMA
struct kmem_cache *temp_kmem_cache_node;
unsigned long kmalloc_size;

kmem_size = offsetof(struct kmem_cache, node) +
nr_node_ids * sizeof(struct kmem_cache_node *);

/* Allocate two kmem_caches from the page allocator */
kmalloc_size = ALIGN(kmem_size, cache_line_size());
order = get_order(2 * kmalloc_size);
kmem_cache = (void *)__get_free_pages(GFP_NOWAIT, order);

/*
* Must first have the slab cache available for the allocations of the
* struct kmem_cache_node's. There is special bootstrap code in
* kmem_cache_open for slab_state == DOWN.
*/
create_kmalloc_cache(&kmalloc_caches[0], "kmem_cache_node",
sizeof(struct kmem_cache_node), 0);
kmalloc_caches[0].refcount = -1;
caches++;
kmem_cache_node = (void *)kmem_cache + kmalloc_size;

kmem_cache_open(kmem_cache_node, "kmem_cache_node",
sizeof(struct kmem_cache_node),
0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);

hotplug_memory_notifier(slab_memory_callback, SLAB_CALLBACK_PRI);
#else
/* Allocate a single kmem_cache from the page allocator */
kmem_size = sizeof(struct kmem_cache);
order = get_order(kmem_size);
kmem_cache = (void *)__get_free_pages(GFP_NOWAIT, order);
#endif

/* Able to allocate the per node structures */
slab_state = PARTIAL;

/* Caches that are not of the two-to-the-power-of size */
if (KMALLOC_MIN_SIZE <= 32) {
create_kmalloc_cache(&kmalloc_caches[1],
"kmalloc-96", 96, 0);
caches++;
}
if (KMALLOC_MIN_SIZE <= 64) {
create_kmalloc_cache(&kmalloc_caches[2],
"kmalloc-192", 192, 0);
caches++;
}
temp_kmem_cache = kmem_cache;
kmem_cache_open(kmem_cache, "kmem_cache", kmem_size,
0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
kmem_cache = kmem_cache_alloc(kmem_cache, GFP_NOWAIT);
memcpy(kmem_cache, temp_kmem_cache, kmem_size);

for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
create_kmalloc_cache(&kmalloc_caches[i],
"kmalloc", 1 << i, 0);
caches++;
}
#ifdef CONFIG_NUMA
/*
* Allocate kmem_cache_node properly from the kmem_cache slab.
* kmem_cache_node is separately allocated so no need to
* update any list pointers.
*/
temp_kmem_cache_node = kmem_cache_node;

kmem_cache_node = kmem_cache_alloc(kmem_cache, GFP_NOWAIT);
memcpy(kmem_cache_node, temp_kmem_cache_node, kmem_size);

kmem_cache_bootstrap_fixup(kmem_cache_node);

caches++;
#else
/*
* kmem_cache has kmem_cache_node embedded and we moved it!
* Update the list heads
*/
INIT_LIST_HEAD(&kmem_cache->local_node.partial);
list_splice(&temp_kmem_cache->local_node.partial, &kmem_cache->local_node.partial);
#ifdef CONFIG_SLUB_DEBUG
INIT_LIST_HEAD(&kmem_cache->local_node.full);
list_splice(&temp_kmem_cache->local_node.full, &kmem_cache->local_node.full);
#endif
#endif
kmem_cache_bootstrap_fixup(kmem_cache);
caches++;
/* Free temporary boot structure */
free_pages((unsigned long)temp_kmem_cache, order);

/* Now we can use the kmem_cache to allocate kmalloc slabs */

/*
* Patch up the size_index table if we have strange large alignment
Expand Down Expand Up @@ -3019,37 +3094,47 @@ void __init kmem_cache_init(void)
size_index[size_index_elem(i)] = 8;
}

/* Caches that are not of the two-to-the-power-of size */
if (KMALLOC_MIN_SIZE <= 32) {
kmalloc_caches[1] = create_kmalloc_cache("kmalloc-96", 96, 0);
caches++;
}

if (KMALLOC_MIN_SIZE <= 64) {
kmalloc_caches[2] = create_kmalloc_cache("kmalloc-192", 192, 0);
caches++;
}

for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
kmalloc_caches[i] = create_kmalloc_cache("kmalloc", 1 << i, 0);
caches++;
}

slab_state = UP;

/* Provide the correct kmalloc names now that the caches are up */
for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
char *s = kasprintf(GFP_NOWAIT, "kmalloc-%d", 1 << i);

BUG_ON(!s);
kmalloc_caches[i].name = s;
kmalloc_caches[i]->name = s;
}

#ifdef CONFIG_SMP
register_cpu_notifier(&slab_notifier);
#endif
#ifdef CONFIG_NUMA
kmem_size = offsetof(struct kmem_cache, node) +
nr_node_ids * sizeof(struct kmem_cache_node *);
#else
kmem_size = sizeof(struct kmem_cache);
#endif

#ifdef CONFIG_ZONE_DMA
for (i = 1; i < SLUB_PAGE_SHIFT; i++) {
struct kmem_cache *s = &kmalloc_caches[i];
for (i = 0; i < SLUB_PAGE_SHIFT; i++) {
struct kmem_cache *s = kmalloc_caches[i];

if (s->size) {
if (s && s->size) {
char *name = kasprintf(GFP_NOWAIT,
"dma-kmalloc-%d", s->objsize);

BUG_ON(!name);
create_kmalloc_cache(&kmalloc_dma_caches[i],
name, s->objsize, SLAB_CACHE_DMA);
kmalloc_dma_caches[i] = create_kmalloc_cache(name,
s->objsize, SLAB_CACHE_DMA);
}
}
#endif
Expand Down

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