On Wed, 25 Aug 2010, Christoph Lameter wrote:
> Since the percpu allocator does not provide early allocation in UP
> mode (only in SMP configurations) use __get_free_page() to improvise
> a compound page allocation that can be later freed via kfree().
>
> Compound pages will be released when the cpu caches are resized.
>
> Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
>
> ---
> mm/slub.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c 2010-08-24 20:07:12.766010774 -0500
> +++ linux-2.6/mm/slub.c 2010-08-24 20:15:46.304130417 -0500
> @@ -2064,8 +2064,24 @@
>
> static inline int alloc_kmem_cache_cpus(struct kmem_cache *s)
> {
> +#ifdef CONFIG_SMP
> + /*
> + * Will use reserve that does not require slab operation during
> + * early boot.
> + */
> BUILD_BUG_ON(PERCPU_DYNAMIC_EARLY_SIZE <
> SLUB_PAGE_SHIFT * sizeof(struct kmem_cache_cpu));
> +#else
> + /*
> + * Special hack for UP mode. allocpercpu() falls back to kmalloc
> + * operations. So we cannot use that before the slab allocator is up
> + * Simply get the smallest possible compound page. The page will be
> + * released via kfree() when the cpu caches are resized later.
> + */
> + if (slab_state < UP)
> + s->cpu_slab = (__percpu void *)__get_free_page(GFP_NOWAIT, 1);
__get_free_pages() takes an order argument.
> + else
> +#endif
>
> s->cpu_slab = alloc_percpu(struct kmem_cache_cpu);
>
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