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Date: Wed, 16 Sep 2015 15:26:28 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Vineet Gupta <Vineet.Gupta1@synopsys.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Mel Gorman <mgorman@suse.de>,
        "Matthew Wilcox" <matthew.r.wilcox@intel.com>,
        Minchan Kim <minchan@kernel.org>, <linux-arch@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
        <arc-linux-dev@synopsys.com>
Subject: Re: [PATCH 09/11] mm,thp: introduce flush_pmd_tlb_range
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On Thu, 27 Aug 2015 14:33:12 +0530 Vineet Gupta <Vineet.Gupta1@synopsys.com> wrote:

> --- a/mm/pgtable-generic.c
> +++ b/mm/pgtable-generic.c
> @@ -84,6 +84,19 @@ pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address,
>  
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  
> +#ifndef __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
> +
> +/*
> + * ARCHes with special requirements for evicting THP backing TLB entries can
> + * implement this. Otherwise also, it can help optimizing thp flush operation.
> + * flush_tlb_range() can have optimization to nuke the entire TLB if flush span
> + * is greater than a threashhold, which will likely be true for a single
> + * huge page.
> + * e.g. see arch/arc: flush_pmd_tlb_range
> + */
> +#define flush_pmd_tlb_range(vma, addr, end)	flush_tlb_range(vma, addr, end)
> +#endif

Did you consider using a __weak function here?