Hi:
On 2021/1/17 23:10, Muchun Song wrote:
> The HUGETLB_PAGE_FREE_VMEMMAP option is used to enable the freeing
> of unnecessary vmemmap associated with HugeTLB pages. 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@xxxxxxxxxxxxx>
> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
> Acked-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> ---
> arch/x86/mm/init_64.c | 2 +-
> fs/Kconfig | 18 ++++++++++++++++++
> 2 files changed, 19 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 976e8b9033c4..e7c4c2a79311 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -245,6 +245,24 @@ 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
> + help
> + 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.
> +
> config MEMFD_CREATE
> def_bool TMPFS || HUGETLBFS
>
>
LGTM. Thanks.
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
