Re: Common10 [16/20] slub: Use a statically allocated kmem_cache boot structure for bootstrap

[JoonSoo Kim <js1304@gmail.com>]

2012/8/4 Christoph Lameter <cl@linux.com>:
> Simplify bootstrap by statically allocated two kmem_cache structures. These are
> freed after bootup is complete. Allows us to no longer worry about calculations
> of sizes of kmem_cache structures during bootstrap.
>
> Reviewed-by: Glauber Costa <glommer@parallels.com>
> Signed-off-by: Christoph Lameter <cl@linux.com>
>
> ---
>  mm/slub.c |   32 +++++++++-----------------------
>  1 file changed, 9 insertions(+), 23 deletions(-)
>
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c    2012-08-03 13:46:46.776520899 -0500
> +++ linux-2.6/mm/slub.c 2012-08-03 13:47:50.005667279 -0500
> @@ -3239,29 +3239,6 @@ static int __init setup_slub_nomerge(cha
>
>  __setup("slub_nomerge", setup_slub_nomerge);
>
> -static struct kmem_cache *__init create_kmalloc_cache(const char *name,
> -                                               int size, unsigned int flags)
> -{
> -       struct kmem_cache *s;
> -
> -       s = kmem_cache_alloc(kmem_cache, GFP_NOWAIT);
> -
> -       /*
> -        * This function is called with IRQs disabled during early-boot on
> -        * single CPU so there's no need to take slab_mutex here.
> -        */
> -       if (!kmem_cache_open(s, name, size, ARCH_KMALLOC_MINALIGN,
> -                                                               flags, NULL))
> -               goto panic;
> -
> -       list_add(&s->list, &slab_caches);
> -       return s;
> -
> -panic:
> -       panic("Creation of kmalloc slab %s size=%d failed.\n", name, size);
> -       return NULL;
> -}
> -
>  /*
>   * Conversion table for small slabs sizes / 8 to the index in the
>   * kmalloc array. This is necessary for slabs < 192 since we have non power
> @@ -3658,9 +3635,6 @@ static void __init kmem_cache_bootstrap_
>  {
>         int node;
>
> -       list_add(&s->list, &slab_caches);
> -       s->refcount = -1;
> -
>         for_each_node_state(node, N_NORMAL_MEMORY) {
>                 struct kmem_cache_node *n = get_node(s, node);
>                 struct page *p;
> @@ -3677,13 +3651,13 @@ static void __init kmem_cache_bootstrap_
>         }
>  }
>
> +static __initdata struct kmem_cache boot_kmem_cache,
> +                       boot_kmem_cache_node;
> +
>  void __init kmem_cache_init(void)
>  {
>         int i;
> -       int caches = 0;
> -       struct kmem_cache *temp_kmem_cache;
> -       int order;
> -       struct kmem_cache *temp_kmem_cache_node;
> +       int caches = 2;
>         unsigned long kmalloc_size;
>
>         if (debug_guardpage_minorder())
> @@ -3692,50 +3666,33 @@ void __init kmem_cache_init(void)
>         kmem_size = offsetof(struct kmem_cache, node) +
>                         nr_node_ids * sizeof(struct kmem_cache_node *);
>
> -       /* Allocate two kmem_caches from the page allocator */
>         kmalloc_size = ALIGN(kmem_size, cache_line_size());
> -       order = get_order(2 * kmalloc_size);
> -       kmem_cache = (void *)__get_free_pages(GFP_NOWAIT, order);
> -
> -       /*
> -        * Must first have the slab cache available for the allocations of the
> -        * struct kmem_cache_node's. There is special bootstrap code in
> -        * kmem_cache_open for slab_state == DOWN.
> -        */
> -       kmem_cache_node = (void *)kmem_cache + kmalloc_size;
> +       kmem_cache_node = &boot_kmem_cache_node;
>
> -       kmem_cache_open(kmem_cache_node, "kmem_cache_node",
> -               sizeof(struct kmem_cache_node),
> -               0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
> +       create_boot_cache(kmem_cache_node, "kmem_cache_node",
> +               sizeof(struct kmem_cache_node), SLAB_HWCACHE_ALIGN);
>
>         hotplug_memory_notifier(slab_memory_callback, SLAB_CALLBACK_PRI);
>
>         /* Able to allocate the per node structures */
>         slab_state = PARTIAL;
>
> -       temp_kmem_cache = kmem_cache;
> -       kmem_cache_open(kmem_cache, "kmem_cache", kmem_size,
> -               0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
> -       kmem_cache = kmem_cache_alloc(kmem_cache, GFP_NOWAIT);
> -       memcpy(kmem_cache, temp_kmem_cache, kmem_size);
> +       create_boot_cache(&boot_kmem_cache, "kmem_cache",
> +                       kmem_size, SLAB_HWCACHE_ALIGN);
> +
> +       kmem_cache = kmem_cache_alloc(&boot_kmem_cache, GFP_NOWAIT);
> +       memcpy(kmem_cache, &boot_kmem_cache, kmem_size);
>
>         /*
>          * Allocate kmem_cache_node properly from the kmem_cache slab.
>          * kmem_cache_node is separately allocated so no need to
>          * update any list pointers.
>          */
> -       temp_kmem_cache_node = kmem_cache_node;
> -
>         kmem_cache_node = kmem_cache_alloc(kmem_cache, GFP_NOWAIT);
> -       memcpy(kmem_cache_node, temp_kmem_cache_node, kmem_size);
> +       memcpy(kmem_cache_node, &boot_kmem_cache_node, kmem_size);
>
>         kmem_cache_bootstrap_fixup(kmem_cache_node);
> -
> -       caches++;
>         kmem_cache_bootstrap_fixup(kmem_cache);
> -       caches++;
> -       /* Free temporary boot structure */
> -       free_pages((unsigned long)temp_kmem_cache, order);
>
>         /* Now we can use the kmem_cache to allocate kmalloc slabs */
>

Currently, there is no create_boot_cache(), although later patch
define it in slab_common.c.
Fix is needed.

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