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Subject: Re: [PATCH v20 7/9] mm: hugetlb: add a kernel parameter
 hugetlb_free_vmemmap
To:     Muchun Song <songmuchun@bytedance.com>, corbet@lwn.net,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org,
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        pawan.kumar.gupta@linux.intel.com, rdunlap@infradead.org,
        oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de,
        almasrymina@google.com, rientjes@google.com, willy@infradead.org,
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        david@redhat.com, naoya.horiguchi@nec.com,
        joao.m.martins@oracle.com
Cc:     duanxiongchun@bytedance.com, fam.zheng@bytedance.com,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        Miaohe Lin <linmiaohe@huawei.com>,
        Chen Huang <chenhuang5@huawei.com>,
        Bodeddula Balasubramaniam <bodeddub@amazon.com>
References: <20210415084005.25049-1-songmuchun@bytedance.com>
 <20210415084005.25049-8-songmuchun@bytedance.com>
From:   Mike Kravetz <mike.kravetz@oracle.com>
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On 4/15/21 1:40 AM, Muchun Song wrote:
> Add a kernel parameter hugetlb_free_vmemmap to enable the feature of
> freeing unused vmemmap pages associated with each hugetlb page on boot.
> 
> We disables PMD mapping of vmemmap pages for x86-64 arch when this
> feature is enabled. Because vmemmap_remap_free() depends on vmemmap
> being base page mapped.
> 
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Reviewed-by: Oscar Salvador <osalvador@suse.de>
> Reviewed-by: Barry Song <song.bao.hua@hisilicon.com>
> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
> Tested-by: Chen Huang <chenhuang5@huawei.com>
> Tested-by: Bodeddula Balasubramaniam <bodeddub@amazon.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 17 +++++++++++++++++
>  Documentation/admin-guide/mm/hugetlbpage.rst    |  3 +++
>  arch/x86/mm/init_64.c                           |  8 ++++++--
>  include/linux/hugetlb.h                         | 19 +++++++++++++++++++
>  mm/hugetlb_vmemmap.c                            | 24 ++++++++++++++++++++++++
>  5 files changed, 69 insertions(+), 2 deletions(-)

Thanks,

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