linux-kernel - Re: [PATCH 1/5] mm: hugetlb: introduce helpers to preallocate/free page tables

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Date:   Thu, 10 Jun 2021 14:49:19 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Muchun Song <songmuchun@...edance.com>, akpm@...ux-foundation.org,
        osalvador@...e.de, mhocko@...e.com, song.bao.hua@...ilicon.com,
        david@...hat.com, chenhuang5@...wei.com, bodeddub@...zon.com,
        corbet@....net
Cc:     duanxiongchun@...edance.com, fam.zheng@...edance.com,
        zhengqi.arch@...edance.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/5] mm: hugetlb: introduce helpers to preallocate/free
 page tables

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@...edance.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@...cle.com>
-- 
Mike Kravetz