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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: Muchun 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Muchun Song 2021-06-30 18:48:28 -07:00 committed by Linus Torvalds
parent 2d7a21715f
commit e6d41f12df
3 changed files with 17 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
Documentation/admin-guide/kernel-parameters.txt
View File

@ -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.

10
fs/Kconfig
View File

@ -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

6
mm/hugetlb_vmemmap.c
View File

@ -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;