The purpose of introducing HUGETLB_PAGE_FREE_VMEMMAP is to configure
whether to enable the feature of freeing unused vmemmap associated
with HugeTLB pages. Now only support x86.
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
arch/x86/mm/init_64.c | 2 +-
fs/Kconfig | 14 ++++++++++++++
2 files changed, 15 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..67e1bc99574f 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -245,6 +245,20 @@ config HUGETLBFS
config HUGETLB_PAGE
def_bool HUGETLBFS
+config HUGETLB_PAGE_FREE_VMEMMAP
+ def_bool HUGETLB_PAGE
+ depends on X86
+ depends on SPARSEMEM_VMEMMAP
+ depends on HAVE_BOOTMEM_INFO_NODE
+ help
+ When using SPARSEMEM_VMEMMAP, the system can save up some memory
+ from pre-allocated HugeTLB pages when they are not used. 6 pages
+ per 2MB HugeTLB page and 4094 per 1GB HugeTLB page.
+
+ When the pages are going to be used or freed up, the vmemmap array
+ representing that range needs to be remapped again and the pages
+ we discarded earlier need to be rellocated again.
+
config MEMFD_CREATE
def_bool TMPFS || HUGETLBFS
--
2.11.0
