Commit e6d41f12 authored by Muchun Song's avatar Muchun Song Committed by Linus Torvalds
Browse files

mm: hugetlb: introduce CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON 

When using HUGETLB_PAGE_FREE_VMEMMAP, the freeing unused vmemmap pages
associated with each HugeTLB page is default off.  Now the vmemmap is PMD
mapped.  So there is no side effect when this feature is enabled with no
HugeTLB pages in the system.  Someone may want to enable this feature in
the compiler time instead of using boot command line.  So add a config to
make it default on when someone do not want to enable it via command line.

Link: https://lkml.kernel.org/r/20210616094915.34432-4-songmuchun@bytedance.com


Signed-off-by: default avatarMuchun Song <songmuchun@bytedance.com>
Cc: Chen Huang <chenhuang5@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2d7a2171

Documentation/admin-guide/kernel-parameters.txt

+3 −0
Original line number Diff line number Diff line
@@ -1577,6 +1577,9 @@ 
			on:  enable the feature

			off: disable the feature



			Built with CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON=y,

			the default is on.



			This is not compatible with memory_hotplug.memmap_on_memory.

			If both parameters are enabled, hugetlb_free_vmemmap takes

			precedence over memory_hotplug.memmap_on_memory.

fs/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -245,6 +245,16 @@ config HUGETLB_PAGE_FREE_VMEMMAP 
	depends on X86_64

	depends on SPARSEMEM_VMEMMAP



config HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON

	bool "Default freeing vmemmap pages of HugeTLB to on"

	default n

	depends on HUGETLB_PAGE_FREE_VMEMMAP

	help

	  When using HUGETLB_PAGE_FREE_VMEMMAP, the freeing unused vmemmap

	  pages associated with each HugeTLB page is default off. Say Y here

	  to enable freeing vmemmap pages of HugeTLB by default. It can then

	  be disabled on the command line via hugetlb_free_vmemmap=off.



config MEMFD_CREATE

	def_bool TMPFS || HUGETLBFS

mm/hugetlb_vmemmap.c

+4 −2
Original line number Diff line number Diff line
@@ -182,7 +182,7 @@ 
#define RESERVE_VMEMMAP_NR		2U

#define RESERVE_VMEMMAP_SIZE		(RESERVE_VMEMMAP_NR << PAGE_SHIFT)



bool hugetlb_free_vmemmap_enabled;

bool hugetlb_free_vmemmap_enabled = IS_ENABLED(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON);



static int __init early_hugetlb_free_vmemmap_param(char *buf)

{
@@ -197,7 +197,9 @@ static int __init early_hugetlb_free_vmemmap_param(char *buf) 


	if (!strcmp(buf, "on"))

		hugetlb_free_vmemmap_enabled = true;

	else if (strcmp(buf, "off"))

	else if (!strcmp(buf, "off"))

		hugetlb_free_vmemmap_enabled = false;

	else

		return -EINVAL;



	return 0;