Commit b5d8ca7c authored by Ravikiran G Thirumalai's avatar Ravikiran G Thirumalai Committed by Linus Torvalds
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[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: default avatarRavikiran 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: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent a737b3e2

mm/slab.c

+9 −11
Original line number Diff line number Diff line
@@ -372,17 +372,19 @@ static void kmem_list3_init(struct kmem_list3 *parent) 
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 @@ struct kmem_cache { 
	/* 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 @@ static struct kmem_cache cache_cache = { 
	.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 @@ kmem_cache_create (const char *name, size_t size, size_t align, 
	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 @@ static void do_ccupdate_local(void *info) 
	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 @@ static int do_tune_cpucache(struct kmem_cache *cachep, int limit, 
	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 @@ static int do_tune_cpucache(struct kmem_cache *cachep, int limit, 
	return 0;

}



/* Called with cache_chain_mutex held always */

static void enable_cpucache(struct kmem_cache *cachep)

{

	int err;
@@ -3705,7 +3705,6 @@ static int s_show(struct seq_file *m, void *p) 
	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 @@ static int s_show(struct seq_file *m, void *p) 
	}

#endif

	seq_putc(m, '\n');

	spin_unlock(&cachep->spinlock);

	return 0;

}

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