[patch 2/3] NUMA slab locking fixes - move irq disabling from cahep->spinlock to l3 lock

Ravikiran G Thirumalai
2006-02-04T01:27:50Z

Earlier, we had to disable on chip interrupts while taking the cachep->spinlock
because, at cache_grow, on every addition of a slab to a slab cache, we
incremented colour_next which was protected by the cachep->spinlock, and
cache_grow could occur at interrupt context. Since, now we protect the
per-node colour_next with the node's list_lock, we do not need to disable
on chip interrupts while taking the per-cache spinlock, but we
just need to disable interrupts when taking the per-node kmem_list3 list_lock.

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-rc2/mm/slab.c
===================================================================
--- linux-2.6.16-rc2.orig/mm/slab.c 2006-02-03 15:07:56.000000000 -0800
+++ linux-2.6.16-rc2/mm/slab.c 2006-02-03 15:10:04.000000000 -0800
@@ -987,7 +987,7 @@ static int __devinit cpuup_callback(stru
cpumask_t mask;

mask = node_to_cpumask(node);
- spin_lock_irq(&cachep->spinlock);
+ spin_lock(&cachep->spinlock);
/* cpu is dead; no one can alloc from it. */
nc = cachep->array[cpu];
cachep->array[cpu] = NULL;
@@ -996,7 +996,7 @@ static int __devinit cpuup_callback(stru
if (!l3)
goto unlock_cache;

- spin_lock(&l3->list_lock);
+ spin_lock_irq(&l3->list_lock);

/* Free limit for this kmem_list3 */
l3->free_limit -= cachep->batchcount;
@@ -1004,7 +1004,7 @@ static int __devinit cpuup_callback(stru
free_block(cachep, nc->entry, nc->avail, node);

if (!cpus_empty(mask)) {
- spin_unlock(&l3->list_lock);
+ spin_unlock_irq(&l3->list_lock);
goto unlock_cache;
}

@@ -1023,13 +1023,13 @@ static int __devinit cpuup_callback(stru
/* free slabs belonging to this node */
if (__node_shrink(cachep, node)) {
cachep->nodelists[node] = NULL;
- spin_unlock(&l3->list_lock);
+ spin_unlock_irq(&l3->list_lock);
kfree(l3);
} else {
- spin_unlock(&l3->list_lock);
+ spin_unlock_irq(&l3->list_lock);
}
unlock_cache:
- spin_unlock_irq(&cachep->spinlock);
+ spin_unlock(&cachep->spinlock);
kfree(nc);
}
mutex_unlock(&cache_chain_mutex);
@@ -2011,18 +2011,18 @@ static void drain_cpu_caches(struct kmem

smp_call_function_all_cpus(do_drain, cachep);
check_irq_on();
- spin_lock_irq(&cachep->spinlock);
+ spin_lock(&cachep->spinlock);
for_each_online_node(node) {
l3 = cachep->nodelists[node];
if (l3) {
- spin_lock(&l3->list_lock);
+ spin_lock_irq(&l3->list_lock);
drain_array_locked(cachep, l3->shared, 1, node);
- spin_unlock(&l3->list_lock);
+ spin_unlock_irq(&l3->list_lock);
if (l3->alien)
drain_alien_cache(cachep, l3);
}
}
- spin_unlock_irq(&cachep->spinlock);
+ spin_unlock(&cachep->spinlock);
}

static int __node_shrink(struct kmem_cache *cachep, int node)
@@ -2338,7 +2338,6 @@ static int cache_grow(struct kmem_cache

offset *= cachep->colour_off;

- check_irq_off();
if (local_flags & __GFP_WAIT)
local_irq_enable();

@@ -2725,6 +2724,7 @@ static void *__cache_alloc_node(struct k
BUG_ON(!l3);

retry:
+ check_irq_off();
spin_lock(&l3->list_lock);
entry = l3->slabs_partial.next;
if (entry == &l3->slabs_partial) {
@@ -3304,11 +3304,11 @@ static int do_tune_cpucache(struct kmem_
smp_call_function_all_cpus(do_ccupdate_local, (void *)&new);

check_irq_on();
- spin_lock_irq(&cachep->spinlock);
+ spin_lock(&cachep->spinlock);
cachep->batchcount = batchcount;
cachep->limit = limit;
cachep->shared = shared;
- spin_unlock_irq(&cachep->spinlock);
+ spin_unlock(&cachep->spinlock);

for_each_online_cpu(i) {
struct array_cache *ccold = new.new[i];
@@ -3564,8 +3564,7 @@ static int s_show(struct seq_file *m, vo
int node;
struct kmem_list3 *l3;

- check_irq_on();
- spin_lock_irq(&cachep->spinlock);
+ spin_lock(&cachep->spinlock);
active_objs = 0;
num_slabs = 0;
for_each_online_node(node) {
@@ -3573,7 +3572,8 @@ static int s_show(struct seq_file *m, vo
if (!l3)
continue;

- spin_lock(&l3->list_lock);
+ check_irq_on();
+ spin_lock_irq(&l3->list_lock);

list_for_each(q, &l3->slabs_full) {
slabp = list_entry(q, struct slab, list);
@@ -3600,7 +3600,7 @@ static int s_show(struct seq_file *m, vo
free_objects += l3->free_objects;
shared_avail += l3->shared->avail;

- spin_unlock(&l3->list_lock);
+ spin_unlock_irq(&l3->list_lock);
}
num_slabs += active_slabs;
num_objs = num_slabs * cachep->num;
@@ -3644,7 +3644,7 @@ static int s_show(struct seq_file *m, vo
}
#endif
seq_putc(m, '\n');
- spin_unlock_irq(&cachep->spinlock);
+ spin_unlock(&cachep->spinlock);
return 0;
}