[patch] slab: resize the alien caches too

[patch] slab: resize the alien caches too

[Siddha, Suresh B]

Christoph,

While going through the slab code, I observed that alien caches are
not getting resized, when user changes the slab tunables. Appended patch
tries to fix this. Please review and let me know if I missed anything.

thanks,
suresh
---

Resize the alien caches too based on the slab tunables.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
---

diff --git a/mm/slab.c b/mm/slab.c
index 4cbac24..e0dd9af 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3823,6 +3823,7 @@ static int alloc_kmemlist(struct kmem_cache *cachep)
 		l3 = cachep->nodelists[node];
 		if (l3) {
 			struct array_cache *shared = l3->shared;
+			struct array_cache **alien = l3->alien;
 
 			spin_lock_irq(&l3->list_lock);
 
@@ -3831,15 +3832,15 @@ static int alloc_kmemlist(struct kmem_cache *cachep)
 						shared->avail, node);
 
 			l3->shared = new_shared;
-			if (!l3->alien) {
-				l3->alien = new_alien;
-				new_alien = NULL;
-			}
+			l3->alien = new_alien;
 			l3->free_limit = (1 + nr_cpus_node(node)) *
 					cachep->batchcount + cachep->num;
 			spin_unlock_irq(&l3->list_lock);
 			kfree(shared);
-			free_alien_cache(new_alien);
+			if (alien) {
+				drain_alien_cache(cachep, alien);
+				free_alien_cache(alien);
+			}
 			continue;
 		}
 		l3 = kmalloc_node(sizeof(struct kmem_list3), GFP_KERNEL, node);

Re: [patch] slab: resize the alien caches too

[Christoph Lameter]

On Tue, 17 Apr 2007, Siddha, Suresh B wrote:

> While going through the slab code, I observed that alien caches are
> not getting resized, when user changes the slab tunables. Appended patch
> tries to fix this. Please review and let me know if I missed anything.

Let it be. We have not resized the alien caches ever and doing so may 
cause serious memory usage. Size is hardcoded to 12 anyways.

Re: [patch] slab: resize the alien caches too

[Siddha, Suresh B]

On Tue, Apr 17, 2007 at 05:48:30PM -0700, Christoph Lameter wrote:
> On Tue, 17 Apr 2007, Siddha, Suresh B wrote:
> 
> > While going through the slab code, I observed that alien caches are
> > not getting resized, when user changes the slab tunables. Appended patch
> > tries to fix this. Please review and let me know if I missed anything.
> 
> Let it be. We have not resized the alien caches ever and doing so may 
> cause serious memory usage. Size is hardcoded to 12 anyways.

hmm.. I see.

Let me do some experiments and getback to you(with what I am looking
exactly).

thanks,
suresh

Re: [patch] slab: resize the alien caches too

[Eric Dumazet]

Siddha, Suresh B a écrit :
> Christoph,
> 
> While going through the slab code, I observed that alien caches are
> not getting resized, when user changes the slab tunables. Appended patch
> tries to fix this. Please review and let me know if I missed anything.
> 
> thanks,
> suresh
> ---
> 
> Resize the alien caches too based on the slab tunables.
> 
> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
> ---
> 
> diff --git a/mm/slab.c b/mm/slab.c
> index 4cbac24..e0dd9af 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -3823,6 +3823,7 @@ static int alloc_kmemlist(struct kmem_cache *cachep)
>  		l3 = cachep->nodelists[node];
>  		if (l3) {
>  			struct array_cache *shared = l3->shared;
> +			struct array_cache **alien = l3->alien;
>  
>  			spin_lock_irq(&l3->list_lock);
>  

Christoph already rejected the patch, but I have one further comment : 
l3->alien should be fetched after spin_lock_irq() of course.

It's true that the :
if (limit > 1) limit = 12;
from alloc_alien_cache() is quite disturbing and could be cleaned up.