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    SubjectRe: [External] Re: [RFC PATCH 03/24] mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE_VMEMMAP
    On Wed, Sep 30, 2020 at 7:41 AM Mike Kravetz <mike.kravetz@oracle.com> wrote:
    >
    > On 9/15/20 5:59 AM, Muchun Song wrote:
    > > The purpose of introducing HUGETLB_PAGE_FREE_VMEMMAP is to configure
    > > whether to enable the feature of freeing unused vmemmap associated
    > > with HugeTLB pages.
    > >
    > > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
    > > ---
    > > fs/Kconfig | 15 +++++++++++++++
    > > 1 file changed, 15 insertions(+)
    > >
    > > diff --git a/fs/Kconfig b/fs/Kconfig
    > > index 976e8b9033c4..61e9c08096ca 100644
    > > --- a/fs/Kconfig
    > > +++ b/fs/Kconfig
    > > @@ -245,6 +245,21 @@ config HUGETLBFS
    > > config HUGETLB_PAGE
    > > def_bool HUGETLBFS
    > >
    > > +config HUGETLB_PAGE_FREE_VMEMMAP
    > > + bool "Free unused vmemmap associated with HugeTLB pages"
    > > + default n
    > > + depends on HUGETLB_PAGE
    > > + depends on SPARSEMEM_VMEMMAP
    > > + depends on HAVE_BOOTMEM_INFO_NODE
    > > + help
    > > + There are many struct page structure associated with each HugeTLB
    > > + page. But we only use a few struct page structure. In this case,
    > > + it waste some memory. It is better to free the unused struct page
    > > + structures to buddy system which can save some memory. For
    > > + architectures that support it, say Y here.
    > > +
    > > + If unsure, say N.
    > > +
    >
    > I could be wrong, but I believe the convention is introduce the config
    > option at the same time code which depends on the option is introduced.
    > Therefore, it might be better to combine with the next patch.

    Yeah, great. Will do that. Thanks.

    >
    > Also, it looks like most of your development was done on x86. Should
    > this option be limited to x86 only for now?

    Now only the x86 has the HAVE_BOOTMEM_INFO_NODE option. So
    maybe this is enough :)

    > --
    > Mike Kravetz



    --
    Yours,
    Muchun

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