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[PATCH] slab: consolidate code to free slabs from freelist
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Post and discussion:
http://marc.theaimsgroup.com/?t=115074342800003&r=1&w=2

Code in __shrink_node() duplicates code in cache_reap()

Add a new function drain_freelist that removes slabs with objects that are
already free and use that in various places.

This eliminates the __node_shrink() function and provides the interrupt
holdoff reduction from slab_free to code that used to call __node_shrink.

[akpm@osdl.org: build fixes]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Christoph Lameter authored and Linus Torvalds committed Jun 30, 2006
1 parent f8891e5 commit ed11d9e
Showing 1 changed file with 51 additions and 68 deletions.
119 changes: 51 additions & 68 deletions mm/slab.c
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Original file line number Diff line number Diff line change
Expand Up @@ -309,6 +309,13 @@ struct kmem_list3 __initdata initkmem_list3[NUM_INIT_LISTS];
#define SIZE_AC 1
#define SIZE_L3 (1 + MAX_NUMNODES)

static int drain_freelist(struct kmem_cache *cache,
struct kmem_list3 *l3, int tofree);
static void free_block(struct kmem_cache *cachep, void **objpp, int len,
int node);
static void enable_cpucache(struct kmem_cache *cachep);
static void cache_reap(void *unused);

/*
* This function must be completely optimized away if a constant is passed to
* it. Mostly the same as what is in linux/slab.h except it returns an index.
Expand Down Expand Up @@ -456,7 +463,7 @@ struct kmem_cache {
#define STATS_DEC_ACTIVE(x) ((x)->num_active--)
#define STATS_INC_ALLOCED(x) ((x)->num_allocations++)
#define STATS_INC_GROWN(x) ((x)->grown++)
#define STATS_INC_REAPED(x) ((x)->reaped++)
#define STATS_ADD_REAPED(x,y) ((x)->reaped += (y))
#define STATS_SET_HIGH(x) \
do { \
if ((x)->num_active > (x)->high_mark) \
Expand All @@ -480,7 +487,7 @@ struct kmem_cache {
#define STATS_DEC_ACTIVE(x) do { } while (0)
#define STATS_INC_ALLOCED(x) do { } while (0)
#define STATS_INC_GROWN(x) do { } while (0)
#define STATS_INC_REAPED(x) do { } while (0)
#define STATS_ADD_REAPED(x,y) do { } while (0)
#define STATS_SET_HIGH(x) do { } while (0)
#define STATS_INC_ERR(x) do { } while (0)
#define STATS_INC_NODEALLOCS(x) do { } while (0)
Expand Down Expand Up @@ -700,12 +707,6 @@ int slab_is_available(void)

static DEFINE_PER_CPU(struct work_struct, reap_work);

static void free_block(struct kmem_cache *cachep, void **objpp, int len,
int node);
static void enable_cpucache(struct kmem_cache *cachep);
static void cache_reap(void *unused);
static int __node_shrink(struct kmem_cache *cachep, int node);

static inline struct array_cache *cpu_cache_get(struct kmem_cache *cachep)
{
return cachep->array[smp_processor_id()];
Expand Down Expand Up @@ -1241,10 +1242,7 @@ static int __devinit cpuup_callback(struct notifier_block *nfb,
l3 = cachep->nodelists[node];
if (!l3)
continue;
spin_lock_irq(&l3->list_lock);
/* free slabs belonging to this node */
__node_shrink(cachep, node);
spin_unlock_irq(&l3->list_lock);
drain_freelist(cachep, l3, l3->free_objects);
}
mutex_unlock(&cache_chain_mutex);
break;
Expand Down Expand Up @@ -2248,32 +2246,45 @@ static void drain_cpu_caches(struct kmem_cache *cachep)
}
}

static int __node_shrink(struct kmem_cache *cachep, int node)
/*
* Remove slabs from the list of free slabs.
* Specify the number of slabs to drain in tofree.
*
* Returns the actual number of slabs released.
*/
static int drain_freelist(struct kmem_cache *cache,
struct kmem_list3 *l3, int tofree)
{
struct list_head *p;
int nr_freed;
struct slab *slabp;
struct kmem_list3 *l3 = cachep->nodelists[node];
int ret;

for (;;) {
struct list_head *p;
nr_freed = 0;
while (nr_freed < tofree && !list_empty(&l3->slabs_free)) {

spin_lock_irq(&l3->list_lock);
p = l3->slabs_free.prev;
if (p == &l3->slabs_free)
break;
if (p == &l3->slabs_free) {
spin_unlock_irq(&l3->list_lock);
goto out;
}

slabp = list_entry(l3->slabs_free.prev, struct slab, list);
slabp = list_entry(p, struct slab, list);
#if DEBUG
BUG_ON(slabp->inuse);
#endif
list_del(&slabp->list);

l3->free_objects -= cachep->num;
/*
* Safe to drop the lock. The slab is no longer linked
* to the cache.
*/
l3->free_objects -= cache->num;
spin_unlock_irq(&l3->list_lock);
slab_destroy(cachep, slabp);
spin_lock_irq(&l3->list_lock);
slab_destroy(cache, slabp);
nr_freed++;
}
ret = !list_empty(&l3->slabs_full) || !list_empty(&l3->slabs_partial);
return ret;
out:
return nr_freed;
}

static int __cache_shrink(struct kmem_cache *cachep)
Expand All @@ -2286,11 +2297,13 @@ static int __cache_shrink(struct kmem_cache *cachep)
check_irq_on();
for_each_online_node(i) {
l3 = cachep->nodelists[i];
if (l3) {
spin_lock_irq(&l3->list_lock);
ret += __node_shrink(cachep, i);
spin_unlock_irq(&l3->list_lock);
}
if (!l3)
continue;

drain_freelist(cachep, l3, l3->free_objects);

ret += !list_empty(&l3->slabs_full) ||
!list_empty(&l3->slabs_partial);
}
return (ret ? 1 : 0);
}
Expand Down Expand Up @@ -3694,10 +3707,6 @@ static void cache_reap(void *unused)
}

list_for_each_entry(searchp, &cache_chain, next) {
struct list_head *p;
int tofree;
struct slab *slabp;

check_irq_on();

/*
Expand All @@ -3722,41 +3731,15 @@ static void cache_reap(void *unused)

drain_array(searchp, l3, l3->shared, 0, node);

if (l3->free_touched) {
if (l3->free_touched)
l3->free_touched = 0;
goto next;
}

tofree = (l3->free_limit + 5 * searchp->num - 1) /
(5 * searchp->num);
do {
/*
* Do not lock if there are no free blocks.
*/
if (list_empty(&l3->slabs_free))
break;

spin_lock_irq(&l3->list_lock);
p = l3->slabs_free.next;
if (p == &(l3->slabs_free)) {
spin_unlock_irq(&l3->list_lock);
break;
}
else {
int freed;

slabp = list_entry(p, struct slab, list);
BUG_ON(slabp->inuse);
list_del(&slabp->list);
STATS_INC_REAPED(searchp);

/*
* Safe to drop the lock. The slab is no longer linked
* to the cache. searchp cannot disappear, we hold
* cache_chain_lock
*/
l3->free_objects -= searchp->num;
spin_unlock_irq(&l3->list_lock);
slab_destroy(searchp, slabp);
} while (--tofree > 0);
freed = drain_freelist(searchp, l3, (l3->free_limit +
5 * searchp->num - 1) / (5 * searchp->num));
STATS_ADD_REAPED(searchp, freed);
}
next:
cond_resched();
}
Expand Down

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