On Thu, Feb 25, 2021 at 09:21:23PM +0800, 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@xxxxxxxxxxxxx> > Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> > Acked-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> > --- Reviewed-by: Balbir Singh <bsingharora@xxxxxxxxx>
