On Wed, 25 Aug 2010, Pekka Enberg wrote:
> I dropped slub cleanups from -next until we've resolved the UP boot time crash
> problem.
>
It works here with this patch. I'd rather see a general solution so that
we can use allocpercpu for bootstrapping any allocator without such
special bandaids.
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.
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);
+ else
+#endif
s->cpu_slab = alloc_percpu(struct kmem_cache_cpu);
--
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