Re: [PATCH 07/50] mm: Account for a THP NUMA hinting update as onePTE update

From: Peter Zijlstra
Date: Mon Sep 16 2013 - 08:37:13 EST


On Tue, Sep 10, 2013 at 10:31:47AM +0100, Mel Gorman wrote:
> A THP PMD update is accounted for as 512 pages updated in vmstat. This is
> large difference when estimating the cost of automatic NUMA balancing and
> can be misleading when comparing results that had collapsed versus split
> THP. This patch addresses the accounting issue.
>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> ---
> mm/mprotect.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index 94722a4..2bbb648 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -145,7 +145,7 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
> split_huge_page_pmd(vma, addr, pmd);
> else if (change_huge_pmd(vma, pmd, addr, newprot,
> prot_numa)) {
> - pages += HPAGE_PMD_NR;
> + pages++;

But now you're not counting pages anymore..
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