[PATCH] slab: remove cachep->spinlock
Remove cachep->spinlock. Locking has moved to the kmem_list3 and most of
the structures protected earlier by cachep->spinlock is now protected by
the l3->list_lock. slab cache tunables like batchcount are accessed always
with the cache_chain_mutex held.
Patch tested on SMP and NUMA kernels with dbench processes running,
constant onlining/offlining, and constant cache tuning, all at the same
time.
Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Cc: Christoph Lameter <christoph@lameter.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/slab.c b/mm/slab.c
index 7b6f9f1..2cd8020 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -372,17 +372,19 @@
struct kmem_cache {
/* 1) per-cpu data, touched during every alloc/free */
struct array_cache *array[NR_CPUS];
+/* 2) Cache tunables. Protected by cache_chain_mutex */
unsigned int batchcount;
unsigned int limit;
unsigned int shared;
+
unsigned int buffer_size;
-/* 2) touched by every alloc & free from the backend */
+/* 3) touched by every alloc & free from the backend */
struct kmem_list3 *nodelists[MAX_NUMNODES];
+
unsigned int flags; /* constant flags */
unsigned int num; /* # of objs per slab */
- spinlock_t spinlock;
-/* 3) cache_grow/shrink */
+/* 4) cache_grow/shrink */
/* order of pgs per slab (2^n) */
unsigned int gfporder;
@@ -401,11 +403,11 @@
/* de-constructor func */
void (*dtor) (void *, struct kmem_cache *, unsigned long);
-/* 4) cache creation/removal */
+/* 5) cache creation/removal */
const char *name;
struct list_head next;
-/* 5) statistics */
+/* 6) statistics */
#if STATS
unsigned long num_active;
unsigned long num_allocations;
@@ -661,7 +663,6 @@
.shared = 1,
.buffer_size = sizeof(struct kmem_cache),
.flags = SLAB_NO_REAP,
- .spinlock = SPIN_LOCK_UNLOCKED,
.name = "kmem_cache",
#if DEBUG
.obj_size = sizeof(struct kmem_cache),
@@ -2057,7 +2058,6 @@
cachep->gfpflags = 0;
if (flags & SLAB_CACHE_DMA)
cachep->gfpflags |= GFP_DMA;
- spin_lock_init(&cachep->spinlock);
cachep->buffer_size = size;
if (flags & CFLGS_OFF_SLAB)
@@ -3425,6 +3425,7 @@
new->new[smp_processor_id()] = old;
}
+/* Always called with the cache_chain_mutex held */
static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
int batchcount, int shared)
{
@@ -3446,11 +3447,9 @@
smp_call_function_all_cpus(do_ccupdate_local, (void *)&new);
check_irq_on();
- spin_lock(&cachep->spinlock);
cachep->batchcount = batchcount;
cachep->limit = limit;
cachep->shared = shared;
- spin_unlock(&cachep->spinlock);
for_each_online_cpu(i) {
struct array_cache *ccold = new.new[i];
@@ -3471,6 +3470,7 @@
return 0;
}
+/* Called with cache_chain_mutex held always */
static void enable_cpucache(struct kmem_cache *cachep)
{
int err;
@@ -3705,7 +3705,6 @@
int node;
struct kmem_list3 *l3;
- spin_lock(&cachep->spinlock);
active_objs = 0;
num_slabs = 0;
for_each_online_node(node) {
@@ -3788,7 +3787,6 @@
}
#endif
seq_putc(m, '\n');
- spin_unlock(&cachep->spinlock);
return 0;
}