On Thu, 1 Nov 2012, Christoph Lameter wrote:
> The nodelists field in kmem_cache is pointing to the first unused
> object in the array field when bootstrap is complete.
>
> A problem with the current approach is that the statically sized
> kmem_cache structure use on boot can only contain NR_CPUS entries.
> If the number of nodes plus the number of cpus is greater then we
> would overwrite memory following the kmem_cache_boot definition.
>
> Increase the size of the array field to ensure that also the node
> pointers fit into the array field.
>
> Once we do that we no longer need the kmem_cache_nodelists
> array and we can then also use that structure elsewhere.
>
> V1->V2:
> - No need to zap kmem_cache->nodelists since it is allocated
> with kmem_cache_zalloc() [glommer]
>
> Acked-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
> Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
> ---
> include/linux/slab_def.h | 2 +-
> mm/slab.c | 18 +++++++++++++-----
> 2 files changed, 14 insertions(+), 6 deletions(-)
>
> Index: linux/include/linux/slab_def.h
> ===================================================================
> --- linux.orig/include/linux/slab_def.h 2012-11-01 10:09:47.073417947 -0500
> +++ linux/include/linux/slab_def.h 2012-11-01 10:09:55.357555494 -0500
> @@ -91,7 +91,7 @@ struct kmem_cache {
> * is statically defined, so we reserve the max number of cpus.
> */
> struct kmem_list3 **nodelists;
> - struct array_cache *array[NR_CPUS];
> + struct array_cache *array[NR_CPUS + MAX_NUMNODES];
Needs to update the comment which specifies this is only sized to NR_CPUS.
> /*
> * Do not add fields after array[]
> */
> Index: linux/mm/slab.c
> ===================================================================
> --- linux.orig/mm/slab.c 2012-11-01 10:09:47.073417947 -0500
> +++ linux/mm/slab.c 2012-11-01 10:09:55.361555562 -0500
> @@ -553,9 +553,7 @@ static struct arraycache_init initarray_
> { {0, BOOT_CPUCACHE_ENTRIES, 1, 0} };
>
> /* internal cache of cache description objs */
> -static struct kmem_list3 *kmem_cache_nodelists[MAX_NUMNODES];
> static struct kmem_cache kmem_cache_boot = {
> - .nodelists = kmem_cache_nodelists,
> .batchcount = 1,
> .limit = BOOT_CPUCACHE_ENTRIES,
> .shared = 1,
> @@ -1560,6 +1558,15 @@ static void __init set_up_list3s(struct
> }
>
> /*
> + * The memory after the last cpu cache pointer is used for the
> + * the nodelists pointer.
> + */
> +static void setup_nodelists_pointer(struct kmem_cache *s)
cachep
> +{
> + s->nodelists = (struct kmem_list3 **)&s->array[nr_cpu_ids];
> +}
> +
> +/*
> * Initialisation. Called after the page allocator have been initialised and
> * before smp_init().
> */
> @@ -1573,15 +1580,14 @@ void __init kmem_cache_init(void)
> int node;
>
> kmem_cache = &kmem_cache_boot;
> + setup_nodelists_pointer(kmem_cache);
>
> if (num_possible_nodes() == 1)
> use_alien_caches = 0;
>
> - for (i = 0; i < NUM_INIT_LISTS; i++) {
> + for (i = 0; i < NUM_INIT_LISTS; i++)
> kmem_list3_init(&initkmem_list3[i]);
> - if (i < MAX_NUMNODES)
> - kmem_cache->nodelists[i] = NULL;
> - }
> +
> set_up_list3s(kmem_cache, CACHE_CACHE);
>
> /*
> @@ -1619,7 +1625,6 @@ void __init kmem_cache_init(void)
> list_add(&kmem_cache->list, &slab_caches);
> kmem_cache->colour_off = cache_line_size();
> kmem_cache->array[smp_processor_id()] = &initarray_cache.cache;
> - kmem_cache->nodelists[node] = &initkmem_list3[CACHE_CACHE + node];
>
> /*
> * struct kmem_cache size depends on nr_node_ids & nr_cpu_ids
> @@ -2425,7 +2430,7 @@ __kmem_cache_create (struct kmem_cache *
> else
> gfp = GFP_NOWAIT;
>
> - cachep->nodelists = (struct kmem_list3 **)&cachep->array[nr_cpu_ids];
> + setup_nodelists_pointer(cachep);
> #if DEBUG
>
> /*
--
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