Re: 2.6.38 page_test regression

[Mel Gorman <mel@csn.ul.ie>]

On Thu, Apr 14, 2011 at 11:07:23PM +0300, raz ben yehuda wrote:
> bah. Mel is correct. I did mean page_test  ( in my defense it is in the
> msg ).
> Here some more information:
> 1. I manage to lower the regression to 2 sha1's:
>     	32dba98e085f8b2b4345887df9abf5e0e93bfc12 to
> 71e3aac0724ffe8918992d76acfe3aad7d8724a5. 
> 	though I had to remark wait_split_huge_page for the sake of
> compilation. up to 32dba98e085f8b2b4345887df9abf5e0e93bfc12 there is no
> regression.
> 
> 2. I booted 2.6.37-rc5 you gave me. same regression is there. 

Extremely long shot - try this patch.

diff --git a/mm/memory.c b/mm/memory.c
index c50a195..a39baaf 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3317,7 +3317,7 @@ int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	 * run pte_offset_map on the pmd, if an huge pmd could
 	 * materialize from under us from a different thread.
 	 */
-	if (unlikely(__pte_alloc(mm, vma, pmd, address)))
+	if (unlikely(!pmd_present(*(pmd))) && __pte_alloc(mm, vma, pmd, address))
 		return VM_FAULT_OOM;
 	/* if an huge pmd materialized from under us just retry later */
 	if (unlikely(pmd_trans_huge(*pmd)))