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SubjectRe: [PATCH v14 2/8] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP
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Hi:
On 2021/2/4 11:50, Muchun Song wrote:
> The option HUGETLB_PAGE_FREE_VMEMMAP allows for the freeing of
> some vmemmap pages associated with pre-allocated HugeTLB pages.
> For example, on X86_64 6 vmemmap pages of size 4KB each can be
> saved for each 2MB HugeTLB page. 4094 vmemmap pages of size 4KB
> each can be saved for each 1GB HugeTLB page.
>
> When a HugeTLB page is allocated or freed, the vmemmap array
> representing the range associated with the page will need to be
> remapped. When a page is allocated, vmemmap pages are freed
> after remapping. When a page is freed, previously discarded
> vmemmap pages must be allocated before remapping.
>
> The config option is introduced early so that supporting code
> can be written to depend on the option. The initial version of
> the code only provides support for x86-64.
>
> Like other code which frees vmemmap, this config option depends on
> HAVE_BOOTMEM_INFO_NODE. The routine register_page_bootmem_info() is
> used to register bootmem info. Therefore, make sure
> register_page_bootmem_info is enabled if HUGETLB_PAGE_FREE_VMEMMAP
> is defined.
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Reviewed-by: Oscar Salvador <osalvador@suse.de>
> Acked-by: Mike Kravetz <mike.kravetz@oracle.com>

LGTM. Thanks.
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>

> ---
> arch/x86/mm/init_64.c | 2 +-
> fs/Kconfig | 6 ++++++
> 2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 0a45f062826e..0435bee2e172 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -1225,7 +1225,7 @@ static struct kcore_list kcore_vsyscall;
>
> static void __init register_page_bootmem_info(void)
> {
> -#ifdef CONFIG_NUMA
> +#if defined(CONFIG_NUMA) || defined(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP)
> int i;
>
> for_each_online_node(i)
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 97e7b77c9309..de87f234f1e9 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -237,6 +237,12 @@ config HUGETLBFS
> config HUGETLB_PAGE
> def_bool HUGETLBFS
>
> +config HUGETLB_PAGE_FREE_VMEMMAP
> + def_bool HUGETLB_PAGE
> + depends on X86_64
> + depends on SPARSEMEM_VMEMMAP
> + depends on HAVE_BOOTMEM_INFO_NODE
> +
> config MEMFD_CREATE
> def_bool TMPFS || HUGETLBFS
>
>

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