[PATCH v3 03/21] mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE_VMEMMAP

[Muchun Song]

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            | 16 ++++++++++++++++
 mm/bootmem_info.c     |  3 +--
 3 files changed, 18 insertions(+), 3 deletions(-)

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..21b8d39a9715 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -245,6 +245,22 @@ config HUGETLBFS
 config HUGETLB_PAGE
 	def_bool HUGETLBFS
 
+config HUGETLB_PAGE_FREE_VMEMMAP
+	bool "Free unused vmemmap associated with HugeTLB pages"
+	default y
+	depends on X86
+	depends on HUGETLB_PAGE
+	depends on SPARSEMEM_VMEMMAP
+	depends on HAVE_BOOTMEM_INFO_NODE
+	help
+	  There are many struct page structures associated with each HugeTLB
+	  page. But we only use a few struct page structures. In this case,
+	  it wastes 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.
+
 config MEMFD_CREATE
 	def_bool TMPFS || HUGETLBFS
 
diff --git a/mm/bootmem_info.c b/mm/bootmem_info.c
index d276e96e487f..fcab5a3f8cc0 100644
--- a/mm/bootmem_info.c
+++ b/mm/bootmem_info.c
@@ -10,8 +10,7 @@
 #include <linux/bootmem_info.h>
 #include <linux/memory_hotplug.h>
 
-void get_page_bootmem(unsigned long info,  struct page *page,
-		      unsigned long type)
+void get_page_bootmem(unsigned long info, struct page *page, unsigned long type)
 {
 	page->freelist = (void *)type;
 	SetPagePrivate(page);
-- 
2.11.0