Re: 2.6.38 page_test regression

From: Mel Gorman
Date: Thu Apr 14 2011 - 17:54:03 EST

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)))
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