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slab: introduce alien_cache
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Currently, we use array_cache for alien_cache.  Although they are mostly
similar, there is one difference, that is, need for spinlock.  We don't
need spinlock for array_cache itself, but to use array_cache for
alien_cache, array_cache structure should have spinlock.  This is
needless overhead, so removing it would be better.  This patch prepare
it by introducing alien_cache and using it.  In the following patch, we
remove spinlock in array_cache.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Joonsoo Kim authored and Linus Torvalds committed Aug 7, 2014
1 parent 1fe00d5 commit c8522a3
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Showing 2 changed files with 68 additions and 42 deletions.
108 changes: 67 additions & 41 deletions mm/slab.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -203,6 +203,11 @@ struct array_cache {
*/
};

struct alien_cache {
spinlock_t lock;
struct array_cache ac;
};

#define SLAB_OBJ_PFMEMALLOC 1
static inline bool is_obj_pfmemalloc(void *objp)
{
Expand Down Expand Up @@ -491,7 +496,7 @@ static void slab_set_lock_classes(struct kmem_cache *cachep,
struct lock_class_key *l3_key, struct lock_class_key *alc_key,
struct kmem_cache_node *n)
{
struct array_cache **alc;
struct alien_cache **alc;
int r;

lockdep_set_class(&n->list_lock, l3_key);
Expand All @@ -507,7 +512,7 @@ static void slab_set_lock_classes(struct kmem_cache *cachep,
return;
for_each_node(r) {
if (alc[r])
lockdep_set_class(&alc[r]->lock, alc_key);
lockdep_set_class(&(alc[r]->ac.lock), alc_key);
}
}

Expand Down Expand Up @@ -965,12 +970,13 @@ static int transfer_objects(struct array_cache *to,
#define drain_alien_cache(cachep, alien) do { } while (0)
#define reap_alien(cachep, n) do { } while (0)

static inline struct array_cache **alloc_alien_cache(int node, int limit, gfp_t gfp)
static inline struct alien_cache **alloc_alien_cache(int node,
int limit, gfp_t gfp)
{
return (struct array_cache **)BAD_ALIEN_MAGIC;
return (struct alien_cache **)BAD_ALIEN_MAGIC;
}

static inline void free_alien_cache(struct array_cache **ac_ptr)
static inline void free_alien_cache(struct alien_cache **ac_ptr)
{
}

Expand All @@ -996,40 +1002,52 @@ static inline void *____cache_alloc_node(struct kmem_cache *cachep,
static void *____cache_alloc_node(struct kmem_cache *, gfp_t, int);
static void *alternate_node_alloc(struct kmem_cache *, gfp_t);

static struct array_cache **alloc_alien_cache(int node, int limit, gfp_t gfp)
static struct alien_cache *__alloc_alien_cache(int node, int entries,
int batch, gfp_t gfp)
{
int memsize = sizeof(void *) * entries + sizeof(struct alien_cache);
struct alien_cache *alc = NULL;

alc = kmalloc_node(memsize, gfp, node);
init_arraycache(&alc->ac, entries, batch);
return alc;
}

static struct alien_cache **alloc_alien_cache(int node, int limit, gfp_t gfp)
{
struct array_cache **ac_ptr;
struct alien_cache **alc_ptr;
int memsize = sizeof(void *) * nr_node_ids;
int i;

if (limit > 1)
limit = 12;
ac_ptr = kzalloc_node(memsize, gfp, node);
if (ac_ptr) {
for_each_node(i) {
if (i == node || !node_online(i))
continue;
ac_ptr[i] = alloc_arraycache(node, limit, 0xbaadf00d, gfp);
if (!ac_ptr[i]) {
for (i--; i >= 0; i--)
kfree(ac_ptr[i]);
kfree(ac_ptr);
return NULL;
}
alc_ptr = kzalloc_node(memsize, gfp, node);
if (!alc_ptr)
return NULL;

for_each_node(i) {
if (i == node || !node_online(i))
continue;
alc_ptr[i] = __alloc_alien_cache(node, limit, 0xbaadf00d, gfp);
if (!alc_ptr[i]) {
for (i--; i >= 0; i--)
kfree(alc_ptr[i]);
kfree(alc_ptr);
return NULL;
}
}
return ac_ptr;
return alc_ptr;
}

static void free_alien_cache(struct array_cache **ac_ptr)
static void free_alien_cache(struct alien_cache **alc_ptr)
{
int i;

if (!ac_ptr)
if (!alc_ptr)
return;
for_each_node(i)
kfree(ac_ptr[i]);
kfree(ac_ptr);
kfree(alc_ptr[i]);
kfree(alc_ptr);
}

static void __drain_alien_cache(struct kmem_cache *cachep,
Expand Down Expand Up @@ -1063,25 +1081,31 @@ static void reap_alien(struct kmem_cache *cachep, struct kmem_cache_node *n)
int node = __this_cpu_read(slab_reap_node);

if (n->alien) {
struct array_cache *ac = n->alien[node];

if (ac && ac->avail && spin_trylock_irq(&ac->lock)) {
__drain_alien_cache(cachep, ac, node);
spin_unlock_irq(&ac->lock);
struct alien_cache *alc = n->alien[node];
struct array_cache *ac;

if (alc) {
ac = &alc->ac;
if (ac->avail && spin_trylock_irq(&ac->lock)) {
__drain_alien_cache(cachep, ac, node);
spin_unlock_irq(&ac->lock);
}
}
}
}

static void drain_alien_cache(struct kmem_cache *cachep,
struct array_cache **alien)
struct alien_cache **alien)
{
int i = 0;
struct alien_cache *alc;
struct array_cache *ac;
unsigned long flags;

for_each_online_node(i) {
ac = alien[i];
if (ac) {
alc = alien[i];
if (alc) {
ac = &alc->ac;
spin_lock_irqsave(&ac->lock, flags);
__drain_alien_cache(cachep, ac, i);
spin_unlock_irqrestore(&ac->lock, flags);
Expand All @@ -1093,7 +1117,8 @@ static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
{
int nodeid = page_to_nid(virt_to_page(objp));
struct kmem_cache_node *n;
struct array_cache *alien = NULL;
struct alien_cache *alien = NULL;
struct array_cache *ac;
int node;
LIST_HEAD(list);

Expand All @@ -1110,13 +1135,14 @@ static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
STATS_INC_NODEFREES(cachep);
if (n->alien && n->alien[nodeid]) {
alien = n->alien[nodeid];
spin_lock(&alien->lock);
if (unlikely(alien->avail == alien->limit)) {
ac = &alien->ac;
spin_lock(&ac->lock);
if (unlikely(ac->avail == ac->limit)) {
STATS_INC_ACOVERFLOW(cachep);
__drain_alien_cache(cachep, alien, nodeid);
__drain_alien_cache(cachep, ac, nodeid);
}
ac_put_obj(cachep, alien, objp);
spin_unlock(&alien->lock);
ac_put_obj(cachep, ac, objp);
spin_unlock(&ac->lock);
} else {
n = get_node(cachep, nodeid);
spin_lock(&n->list_lock);
Expand Down Expand Up @@ -1191,7 +1217,7 @@ static void cpuup_canceled(long cpu)
list_for_each_entry(cachep, &slab_caches, list) {
struct array_cache *nc;
struct array_cache *shared;
struct array_cache **alien;
struct alien_cache **alien;
LIST_HEAD(list);

/* cpu is dead; no one can alloc from it. */
Expand Down Expand Up @@ -1272,7 +1298,7 @@ static int cpuup_prepare(long cpu)
list_for_each_entry(cachep, &slab_caches, list) {
struct array_cache *nc;
struct array_cache *shared = NULL;
struct array_cache **alien = NULL;
struct alien_cache **alien = NULL;

nc = alloc_arraycache(node, cachep->limit,
cachep->batchcount, GFP_KERNEL);
Expand Down Expand Up @@ -3762,7 +3788,7 @@ static int alloc_kmem_cache_node(struct kmem_cache *cachep, gfp_t gfp)
int node;
struct kmem_cache_node *n;
struct array_cache *new_shared;
struct array_cache **new_alien = NULL;
struct alien_cache **new_alien = NULL;

for_each_online_node(node) {

Expand Down
2 changes: 1 addition & 1 deletion mm/slab.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -276,7 +276,7 @@ struct kmem_cache_node {
unsigned int free_limit;
unsigned int colour_next; /* Per-node cache coloring */
struct array_cache *shared; /* shared per node */
struct array_cache **alien; /* on other nodes */
struct alien_cache **alien; /* on other nodes */
unsigned long next_reap; /* updated without locking */
int free_touched; /* updated without locking */
#endif
Expand Down

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