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Subject[RFC] remove page_table_lock in anon_vma_prepare
Date
As I looked over the page_table_lock, it related to page table not anon_vma

I think anon_vma->lock can protect race against threads.
Do I miss something ?

If I am right, we can remove unnecessary page_table_lock holding
in anon_vma_prepare. We can get performance benefit.

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Rik van Riel <riel@redhat.com>
Cc: Nick Piggin <npiggin@suse.de>
---
mm/rmap.c | 3 ---
1 files changed, 0 insertions(+), 3 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index b5c6e12..65b4877 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -113,14 +113,11 @@ int anon_vma_prepare(struct vm_area_struct *vma)
}
spin_lock(&anon_vma->lock);

- /* page_table_lock to protect against threads */
- spin_lock(&mm->page_table_lock);
if (likely(!vma->anon_vma)) {
vma->anon_vma = anon_vma;
list_add_tail(&vma->anon_vma_node, &anon_vma->head);
allocated = NULL;
}
- spin_unlock(&mm->page_table_lock);

spin_unlock(&anon_vma->lock);
if (unlikely(allocated))
--
1.5.6.5


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