Re: [RFC patch] mm: hugetlb: fix __unmap_hugepage_range

[David Rientjes]

On Fri, 31 Oct 2014, Hillf Danton wrote:

> First, after flushing TLB, we have no need to scan pte from start again.
> Second, before bail out loop, the address is forwarded one step.
> 
> Signed-off-by: Hillf Danton 

Acked-by: David Rientjes 
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Re: [RFC patch] mm: hugetlb: fix __unmap_hugepage_range

[Michal Hocko]

[CCing people involved in 24669e58477e2]

On Fri 31-10-14 12:22:12, Hillf Danton wrote:
> First, after flushing TLB, we have no need to scan pte from start again.
> Second, before bail out loop, the address is forwarded one step.

I can imagine a more comprehensive wording here. It is not immediately
clear whether this is just an optimization or a bug fix as well
(especially the second part).

Anyway the optimization looks good to me.

> Signed-off-by: Hillf Danton 

Reviewed-by: Michal Hocko 

> ---
> 
> --- a/mm/hugetlb.cFri Oct 31 11:47:25 2014
> +++ b/mm/hugetlb.cFri Oct 31 11:52:42 2014
> @@ -2641,8 +2641,9 @@ void __unmap_hugepage_range(struct mmu_g
>  
>   tlb_start_vma(tlb, vma);
>   mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
> + address = start;
>  again:
> - for (address = start; address < end; address += sz) {
> + for (; address < end; address += sz) {
>   ptep = huge_pte_offset(mm, address);
>   if (!ptep)
>   continue;
> @@ -2689,6 +2690,7 @@ again:
>   page_remove_rmap(page);
>   force_flush = !__tlb_remove_page(tlb, page);
>   if (force_flush) {
> + address += sz;
>   spin_unlock(ptl);
>   break;
>   }
> --
> 
> 

-- 
Michal Hocko
SUSE Labs
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[RFC patch] mm: hugetlb: fix __unmap_hugepage_range

[Hillf Danton]

First, after flushing TLB, we have no need to scan pte from start again.
Second, before bail out loop, the address is forwarded one step.

Signed-off-by: Hillf Danton 
---

--- a/mm/hugetlb.c  Fri Oct 31 11:47:25 2014
+++ b/mm/hugetlb.c  Fri Oct 31 11:52:42 2014
@@ -2641,8 +2641,9 @@ void __unmap_hugepage_range(struct mmu_g
 
tlb_start_vma(tlb, vma);
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
+   address = start;
 again:
-   for (address = start; address < end; address += sz) {
+   for (; address < end; address += sz) {
ptep = huge_pte_offset(mm, address);
if (!ptep)
continue;
@@ -2689,6 +2690,7 @@ again:
page_remove_rmap(page);
force_flush = !__tlb_remove_page(tlb, page);
if (force_flush) {
+   address += sz;
spin_unlock(ptl);
break;
}
--


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