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Subject: Re: [PATCH 1/5] mm: hugetlb: introduce helpers to preallocate/free
 page tables
To:     Muchun Song <songmuchun@bytedance.com>, akpm@linux-foundation.org,
        osalvador@suse.de, mhocko@suse.com, song.bao.hua@hisilicon.com,
        david@redhat.com, chenhuang5@huawei.com, bodeddub@amazon.com,
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Cc:     duanxiongchun@bytedance.com, fam.zheng@bytedance.com,
        zhengqi.arch@bytedance.com, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
References: <20210609121310.62229-1-songmuchun@bytedance.com>
 <20210609121310.62229-2-songmuchun@bytedance.com>
From:   Mike Kravetz <mike.kravetz@oracle.com>
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On 6/9/21 5:13 AM, Muchun Song wrote:
> On some architectures (e.g. x86_64 and arm64), vmemmap pages are usually
> mapped with huge pmd. We will disable the huge pmd mapping of vmemmap
> pages when the feature of "Free vmemmap pages of HugeTLB page" is enabled.
> This can affect the non-HugeTLB pages. What we want is only mapping the
> vmemmap pages associated with HugeTLB pages with base page. We can split
> the huge pmd mapping of vmemmap pages when freeing vmemmap pages of
> HugeTLB page. But we need to preallocate page tables. In this patch, we
> introduce page tables allocationg/freeing helpers.
> 
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
>  mm/hugetlb_vmemmap.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  mm/hugetlb_vmemmap.h | 12 ++++++++++++
>  2 files changed, 66 insertions(+)

These helper routines are pretty straight forward.

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
-- 
Mike Kravetz