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mm: hugetlb: replace hugetlb_free_vmemmap_enabled with a static_key

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The page_fixed_fake_head() is used throughout memory management and the
conditional check requires checking a global variable, although the
overhead of this check may be small, it increases when the memory cache
comes under pressure.  Also, the global variable will not be modified
after system boot, so it is very appropriate to use static key machanism.

Link: https://lkml.kernel.org/r/20211101031651.75851-3-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Barry Song <song.bao.hua@hisilicon.com>
Cc: Bodeddula Balasubramaniam <bodeddub@amazon.com>
Cc: Chen Huang <chenhuang5@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Fam Zheng <fam.zheng@bytedance.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
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 2022-03-22 14:45:03 -07:00 committed by Linus Torvalds
parent e7d324850b
commit a6b40850c4
4 changed files with 21 additions and 15 deletions
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6
include/linux/hugetlb.h
View File

@ -1075,12 +1075,6 @@ static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr
}
#endif /* CONFIG_HUGETLB_PAGE */
#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
extern bool hugetlb_free_vmemmap_enabled;
#else
#define hugetlb_free_vmemmap_enabled false
#endif
static inline spinlock_t *huge_pte_lock(struct hstate *h,
struct mm_struct *mm, pte_t *pte)
{

16
include/linux/page-flags.h
View File

@ -191,7 +191,14 @@ enum pageflags {
#ifndef __GENERATING_BOUNDS_H
#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
extern bool hugetlb_free_vmemmap_enabled;
DECLARE_STATIC_KEY_MAYBE(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON,
hugetlb_free_vmemmap_enabled_key);
static __always_inline bool hugetlb_free_vmemmap_enabled(void)
{
return static_branch_maybe(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON,
&hugetlb_free_vmemmap_enabled_key);
}
/*
* If the feature of freeing some vmemmap pages associated with each HugeTLB
@ -211,7 +218,7 @@ extern bool hugetlb_free_vmemmap_enabled;
*/
static __always_inline const struct page *page_fixed_fake_head(const struct page *page)
{
if (!hugetlb_free_vmemmap_enabled)
if (!hugetlb_free_vmemmap_enabled())
return page;
/*
@ -239,6 +246,11 @@ static inline const struct page *page_fixed_fake_head(const struct page *page)
{
return page;
}
static inline bool hugetlb_free_vmemmap_enabled(void)
{
return false;
}
#endif
static __always_inline int page_is_fake_head(struct page *page)

12
mm/hugetlb_vmemmap.c
View File

@ -188,9 +188,9 @@
#define RESERVE_VMEMMAP_NR 1U
#define RESERVE_VMEMMAP_SIZE (RESERVE_VMEMMAP_NR << PAGE_SHIFT)
bool hugetlb_free_vmemmap_enabled __read_mostly =
IS_ENABLED(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON);
EXPORT_SYMBOL(hugetlb_free_vmemmap_enabled);
DEFINE_STATIC_KEY_MAYBE(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON,
hugetlb_free_vmemmap_enabled_key);
EXPORT_SYMBOL(hugetlb_free_vmemmap_enabled_key);
static int __init early_hugetlb_free_vmemmap_param(char *buf)
{
@ -204,9 +204,9 @@ static int __init early_hugetlb_free_vmemmap_param(char *buf)
return -EINVAL;
if (!strcmp(buf, "on"))
hugetlb_free_vmemmap_enabled = true;
static_branch_enable(&hugetlb_free_vmemmap_enabled_key);
else if (!strcmp(buf, "off"))
hugetlb_free_vmemmap_enabled = false;
static_branch_disable(&hugetlb_free_vmemmap_enabled_key);
else
return -EINVAL;
@ -284,7 +284,7 @@ void __init hugetlb_vmemmap_init(struct hstate *h)
BUILD_BUG_ON(__NR_USED_SUBPAGE >=
RESERVE_VMEMMAP_SIZE / sizeof(struct page));
if (!hugetlb_free_vmemmap_enabled)
if (!hugetlb_free_vmemmap_enabled())
return;
vmemmap_pages = (nr_pages * sizeof(struct page)) >> PAGE_SHIFT;

2
mm/memory_hotplug.c
View File

@ -1327,7 +1327,7 @@ bool mhp_supports_memmap_on_memory(unsigned long size)
* populate a single PMD.
*/
return memmap_on_memory &&
!hugetlb_free_vmemmap_enabled &&
!hugetlb_free_vmemmap_enabled() &&
IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) &&
size == memory_block_size_bytes() &&
IS_ALIGNED(vmemmap_size, PMD_SIZE) &&