[patch 1/3] NUMA slab locking fixes -- slab-colour-next fix

Ravikiran G Thirumalai
2006-02-03T20:55:08Z

colour_next is used as an index to add a colouring offset to a new slab
in the cache (colour_off * colour_next). Now with the NUMA aware slab
allocator, it makes sense to colour slabs added on the same node
sequentially with colour_next.

This patch moves the colouring index "colour_next" per-node by placing it
on kmem_list3 rather than kmem_cache.

This also avoids taking the cachep->spinlock on the alloc path at
cache_grow.

Signed-off-by: Alok N Kataria <alokk@calsoftinc.com>
Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: Shai Fultheim <shai@scalex86.org>

Index: linux-2.6.16-rc1mm4/mm/slab.c
===================================================================
--- linux-2.6.16-rc1mm4.orig/mm/slab.c 2006-01-29 20:20:20.000000000 -0800
+++ linux-2.6.16-rc1mm4/mm/slab.c 2006-01-29 20:23:28.000000000 -0800
@@ -294,6 +294,7 @@ struct kmem_list3 {
unsigned long next_reap;
int free_touched;
unsigned int free_limit;
+ unsigned int colour_next; /* Per-node cache coloring */
spinlock_t list_lock;
struct array_cache *shared; /* shared per node */
struct array_cache **alien; /* on other nodes */
@@ -344,6 +345,7 @@ static void kmem_list3_init(struct kmem_
INIT_LIST_HEAD(&parent->slabs_free);
parent->shared = NULL;
parent->alien = NULL;
+ parent->colour_next = 0;
spin_lock_init(&parent->list_lock);
parent->free_objects = 0;
parent->free_touched = 0;
@@ -390,7 +392,6 @@ struct kmem_cache {

size_t colour; /* cache colouring range */
unsigned int colour_off; /* colour offset */
- unsigned int colour_next; /* cache colouring */
struct kmem_cache *slabp_cache;
unsigned int slab_size;
unsigned int dflags; /* dynamic flags */
@@ -1127,7 +1128,6 @@ void __init kmem_cache_init(void)
BUG();

cache_cache.colour = left_over / cache_cache.colour_off;
- cache_cache.colour_next = 0;
cache_cache.slab_size = ALIGN(cache_cache.num * sizeof(kmem_bufctl_t) +
sizeof(struct slab), cache_line_size());

@@ -2334,18 +2334,19 @@ static int cache_grow(struct kmem_cache
*/
ctor_flags |= SLAB_CTOR_ATOMIC;

- /* About to mess with non-constant members - lock. */
+ /* Take the l3 list lock to change the colour_next on this node */
check_irq_off();
- spin_lock(&cachep->spinlock);
+ l3 = cachep->nodelists[nodeid];
+ spin_lock(&l3->list_lock);

/* Get colour for the slab, and cal the next value. */
- offset = cachep->colour_next;
- cachep->colour_next++;
- if (cachep->colour_next >= cachep->colour)
- cachep->colour_next = 0;
- offset *= cachep->colour_off;
+ offset = l3->colour_next;
+ l3->colour_next++;
+ if (l3->colour_next >= cachep->colour)
+ l3->colour_next = 0;
+ spin_unlock(&l3->list_lock);

- spin_unlock(&cachep->spinlock);
+ offset *= cachep->colour_off;

check_irq_off();
if (local_flags & __GFP_WAIT)
@@ -2377,7 +2378,6 @@ static int cache_grow(struct kmem_cache
if (local_flags & __GFP_WAIT)
local_irq_disable();
check_irq_off();
- l3 = cachep->nodelists[nodeid];
spin_lock(&l3->list_lock);

/* Make slab active. */