On Wed, 25 Aug 2010, David Rientjes wrote:
> I'm really hoping that we can remove this hack soon when the percpu
> allocator can handle these allocations on UP without any specialized slab
> behavior.
So do I. Here is a slightly less hacky version through using
kmalloc_large instead:
Subject: Slub: UP bandaid
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.
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
---
mm/slub.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c 2010-08-26 09:19:35.000000000 -0500
+++ linux-2.6/mm/slub.c 2010-08-26 09:36:29.000000000 -0500
@@ -2103,8 +2103,24 @@ init_kmem_cache_node(struct kmem_cache_n
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 *)kmalloc_large(PAGE_SIZE << 1, GFP_NOWAIT);
+ else
+#endif
s->cpu_slab = alloc_percpu(struct kmem_cache_cpu);
--
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