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Subject: Re: [PATCH v7 0/5] Free the 2nd vmemmap page associated with each
 HugeTLB page
To:     Muchun Song <songmuchun@bytedance.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oscar Salvador <osalvador@suse.de>,
        Michal Hocko <mhocko@suse.com>,
        David Hildenbrand <david@redhat.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Matthew Wilcox <willy@infradead.org>
Cc:     Xiongchun duan <duanxiongchun@bytedance.com>,
        fam.zheng@bytedance.com, Muchun Song <smuchun@gmail.com>,
        Qi Zheng <zhengqi.arch@bytedance.com>,
        linux-doc@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>,
        Barry Song <21cnbao@gmail.com>,
        Chen Huang <chenhuang5@huawei.com>,
        "Bodeddula, Balasubramaniam" <bodeddub@amazon.com>
References: <20211101031651.75851-1-songmuchun@bytedance.com>
 <CAMZfGtUeL45=WG3ceaZ_tALMGZTLtuD9jbfKEzeQv270OnaLYQ@mail.gmail.com>
From:   Mike Kravetz <mike.kravetz@oracle.com>
Message-ID: <35c5217d-eb8f-6f70-544a-a3e8bd009a46@oracle.com>
Date:   Mon, 8 Nov 2021 11:33:08 -0800
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On 11/8/21 12:16 AM, Muchun Song wrote:
> On Mon, Nov 1, 2021 at 11:22 AM Muchun Song <songmuchun@bytedance.com> wrote:
>>
>> This series can minimize the overhead of struct page for 2MB HugeTLB pages
>> significantly. It further reduces the overhead of struct page by 12.5% for
>> a 2MB HugeTLB compared to the previous approach, which means 2GB per 1TB
>> HugeTLB. It is a nice gain. Comments and reviews are welcome. Thanks.
>>
> 
> Hi,
> 
> Ping guys. Does anyone have any comments or suggestions
> on this series?
> 
> Thanks.
> 

I did look over the series earlier.  I have no issue with the hugetlb and
vmemmap modifications as they are enhancements to the existing
optimizations.  My primary concern is the (small) increased overhead
for the helpers as outlined in your cover letter.  Since these helpers
are not limited to hugetlb and used throughout the kernel, I would
really like to get comments from others with a better understanding of
the potential impact.

-- 
Mike Kravetz