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mm: hugetlb_vmemmap: optimize vmemmap_optimize_mode handling

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We hold an another reference to hugetlb_optimize_vmemmap_key when making
vmemmap_optimize_mode on, because we use static_key to tell memory_hotplug
that memory_hotplug.memmap_on_memory should be overridden.  However, this
rule has gone when we have introduced PageVmemmapSelfHosted.  Therefore,
we could simplify vmemmap_optimize_mode handling by not holding an another
reference to hugetlb_optimize_vmemmap_key.  This also means that we not
incur the extra page_fixed_fake_head checks if there are no vmemmap
optinmized hugetlb pages after this change.

Link: https://lkml.kernel.org/r/20220628092235.91270-3-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Will Deacon <will@kernel.org>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Muchun Song 2022-06-28 17:22:29 +08:00 committed by Andrew Morton
parent 2da1c30929
commit cf5472e561
2 changed files with 9 additions and 62 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
include/linux/page-flags.h
View file

@ -205,8 +205,7 @@ enum pageflags {
#ifndef __GENERATING_BOUNDS_H
#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
DECLARE_STATIC_KEY_MAYBE(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON,
hugetlb_optimize_vmemmap_key);
DECLARE_STATIC_KEY_FALSE(hugetlb_optimize_vmemmap_key);
/*
* If the feature of optimizing vmemmap pages associated with each HugeTLB
@ -226,8 +225,7 @@ DECLARE_STATIC_KEY_MAYBE(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON,
*/
static __always_inline const struct page *page_fixed_fake_head(const struct page *page)
{
if (!static_branch_maybe(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON,
&hugetlb_optimize_vmemmap_key))
if (!static_branch_unlikely(&hugetlb_optimize_vmemmap_key))
return page;
/*

65
mm/hugetlb_vmemmap.c
View file

@ -23,42 +23,15 @@
#define RESERVE_VMEMMAP_NR 1U
#define RESERVE_VMEMMAP_SIZE (RESERVE_VMEMMAP_NR << PAGE_SHIFT)
enum vmemmap_optimize_mode {
VMEMMAP_OPTIMIZE_OFF,
VMEMMAP_OPTIMIZE_ON,
};
DEFINE_STATIC_KEY_MAYBE(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON,
hugetlb_optimize_vmemmap_key);
DEFINE_STATIC_KEY_FALSE(hugetlb_optimize_vmemmap_key);
EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key);
static enum vmemmap_optimize_mode vmemmap_optimize_mode =
static bool vmemmap_optimize_enabled =
IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON);
static void vmemmap_optimize_mode_switch(enum vmemmap_optimize_mode to)
{
if (vmemmap_optimize_mode == to)
return;
if (to == VMEMMAP_OPTIMIZE_OFF)
static_branch_dec(&hugetlb_optimize_vmemmap_key);
else
static_branch_inc(&hugetlb_optimize_vmemmap_key);
WRITE_ONCE(vmemmap_optimize_mode, to);
}
static int __init hugetlb_vmemmap_early_param(char *buf)
{
bool enable;
enum vmemmap_optimize_mode mode;
if (kstrtobool(buf, &enable))
return -EINVAL;
mode = enable ? VMEMMAP_OPTIMIZE_ON : VMEMMAP_OPTIMIZE_OFF;
vmemmap_optimize_mode_switch(mode);
return 0;
return kstrtobool(buf, &vmemmap_optimize_enabled);
}
early_param("hugetlb_free_vmemmap", hugetlb_vmemmap_early_param);
@ -100,7 +73,7 @@ int hugetlb_vmemmap_alloc(struct hstate *h, struct page *head)
static unsigned int vmemmap_optimizable_pages(struct hstate *h,
struct page *head)
{
if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF)
if (!READ_ONCE(vmemmap_optimize_enabled))
return 0;
if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) {
@ -191,7 +164,6 @@ void __init hugetlb_vmemmap_init(struct hstate *h)
if (!is_power_of_2(sizeof(struct page))) {
pr_warn_once("cannot optimize vmemmap pages because \"struct page\" crosses page boundaries\n");
static_branch_disable(&hugetlb_optimize_vmemmap_key);
return;
}
@ -212,36 +184,13 @@ void __init hugetlb_vmemmap_init(struct hstate *h)
}
#ifdef CONFIG_PROC_SYSCTL
static int hugetlb_optimize_vmemmap_handler(struct ctl_table *table, int write,
void *buffer, size_t *length,
loff_t *ppos)
{
int ret;
enum vmemmap_optimize_mode mode;
static DEFINE_MUTEX(sysctl_mutex);
if (write && !capable(CAP_SYS_ADMIN))
return -EPERM;
mutex_lock(&sysctl_mutex);
mode = vmemmap_optimize_mode;
table->data = &mode;
ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
if (write && !ret)
vmemmap_optimize_mode_switch(mode);
mutex_unlock(&sysctl_mutex);
return ret;
}
static struct ctl_table hugetlb_vmemmap_sysctls[] = {
{
.procname = "hugetlb_optimize_vmemmap",
.maxlen = sizeof(enum vmemmap_optimize_mode),
.data = &vmemmap_optimize_enabled,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = hugetlb_optimize_vmemmap_handler,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
.proc_handler = proc_dobool,
},
{ }
};