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![Mike Rapoport](/assets/img/avatar_default.png)
so it will be consistent with code mm directory and with Documentation/admin-guide/mm and won't be confused with virtual machines. Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> Suggested-by: Matthew Wilcox <willy@infradead.org> Tested-by: Ira Weiny <ira.weiny@intel.com> Acked-by: Jonathan Corbet <corbet@lwn.net> Acked-by: Wu XiangCheng <bobwxc@email.cn>
211 lines
6.2 KiB
C
211 lines
6.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Optimize vmemmap pages associated with HugeTLB
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*
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* Copyright (c) 2020, Bytedance. All rights reserved.
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*
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* Author: Muchun Song <songmuchun@bytedance.com>
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*
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* See Documentation/mm/vmemmap_dedup.rst
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*/
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#define pr_fmt(fmt) "HugeTLB: " fmt
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#include <linux/memory_hotplug.h>
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#include "hugetlb_vmemmap.h"
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/*
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* There are a lot of struct page structures associated with each HugeTLB page.
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* For tail pages, the value of compound_head is the same. So we can reuse first
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* page of head page structures. We map the virtual addresses of all the pages
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* of tail page structures to the head page struct, and then free these page
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* frames. Therefore, we need to reserve one pages as vmemmap areas.
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*/
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#define RESERVE_VMEMMAP_NR 1U
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#define RESERVE_VMEMMAP_SIZE (RESERVE_VMEMMAP_NR << PAGE_SHIFT)
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enum vmemmap_optimize_mode {
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VMEMMAP_OPTIMIZE_OFF,
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VMEMMAP_OPTIMIZE_ON,
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};
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DEFINE_STATIC_KEY_MAYBE(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON,
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hugetlb_optimize_vmemmap_key);
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EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key);
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static enum vmemmap_optimize_mode vmemmap_optimize_mode =
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IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON);
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static void vmemmap_optimize_mode_switch(enum vmemmap_optimize_mode to)
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{
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if (vmemmap_optimize_mode == to)
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return;
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if (to == VMEMMAP_OPTIMIZE_OFF)
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static_branch_dec(&hugetlb_optimize_vmemmap_key);
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else
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static_branch_inc(&hugetlb_optimize_vmemmap_key);
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WRITE_ONCE(vmemmap_optimize_mode, to);
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}
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static int __init hugetlb_vmemmap_early_param(char *buf)
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{
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bool enable;
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enum vmemmap_optimize_mode mode;
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if (kstrtobool(buf, &enable))
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return -EINVAL;
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mode = enable ? VMEMMAP_OPTIMIZE_ON : VMEMMAP_OPTIMIZE_OFF;
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vmemmap_optimize_mode_switch(mode);
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return 0;
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}
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early_param("hugetlb_free_vmemmap", hugetlb_vmemmap_early_param);
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/*
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* Previously discarded vmemmap pages will be allocated and remapping
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* after this function returns zero.
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*/
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int hugetlb_vmemmap_alloc(struct hstate *h, struct page *head)
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{
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int ret;
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unsigned long vmemmap_addr = (unsigned long)head;
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unsigned long vmemmap_end, vmemmap_reuse, vmemmap_pages;
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if (!HPageVmemmapOptimized(head))
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return 0;
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vmemmap_addr += RESERVE_VMEMMAP_SIZE;
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vmemmap_pages = hugetlb_optimize_vmemmap_pages(h);
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vmemmap_end = vmemmap_addr + (vmemmap_pages << PAGE_SHIFT);
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vmemmap_reuse = vmemmap_addr - PAGE_SIZE;
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/*
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* The pages which the vmemmap virtual address range [@vmemmap_addr,
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* @vmemmap_end) are mapped to are freed to the buddy allocator, and
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* the range is mapped to the page which @vmemmap_reuse is mapped to.
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* When a HugeTLB page is freed to the buddy allocator, previously
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* discarded vmemmap pages must be allocated and remapping.
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*/
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ret = vmemmap_remap_alloc(vmemmap_addr, vmemmap_end, vmemmap_reuse,
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GFP_KERNEL | __GFP_NORETRY | __GFP_THISNODE);
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if (!ret) {
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ClearHPageVmemmapOptimized(head);
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static_branch_dec(&hugetlb_optimize_vmemmap_key);
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}
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return ret;
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}
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void hugetlb_vmemmap_free(struct hstate *h, struct page *head)
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{
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unsigned long vmemmap_addr = (unsigned long)head;
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unsigned long vmemmap_end, vmemmap_reuse, vmemmap_pages;
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vmemmap_pages = hugetlb_optimize_vmemmap_pages(h);
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if (!vmemmap_pages)
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return;
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if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF)
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return;
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static_branch_inc(&hugetlb_optimize_vmemmap_key);
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vmemmap_addr += RESERVE_VMEMMAP_SIZE;
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vmemmap_end = vmemmap_addr + (vmemmap_pages << PAGE_SHIFT);
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vmemmap_reuse = vmemmap_addr - PAGE_SIZE;
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/*
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* Remap the vmemmap virtual address range [@vmemmap_addr, @vmemmap_end)
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* to the page which @vmemmap_reuse is mapped to, then free the pages
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* which the range [@vmemmap_addr, @vmemmap_end] is mapped to.
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*/
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if (vmemmap_remap_free(vmemmap_addr, vmemmap_end, vmemmap_reuse))
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static_branch_dec(&hugetlb_optimize_vmemmap_key);
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else
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SetHPageVmemmapOptimized(head);
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}
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void __init hugetlb_vmemmap_init(struct hstate *h)
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{
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unsigned int nr_pages = pages_per_huge_page(h);
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unsigned int vmemmap_pages;
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/*
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* There are only (RESERVE_VMEMMAP_SIZE / sizeof(struct page)) struct
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* page structs that can be used when CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP,
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* so add a BUILD_BUG_ON to catch invalid usage of the tail struct page.
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*/
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BUILD_BUG_ON(__NR_USED_SUBPAGE >=
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RESERVE_VMEMMAP_SIZE / sizeof(struct page));
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if (!is_power_of_2(sizeof(struct page))) {
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pr_warn_once("cannot optimize vmemmap pages because \"struct page\" crosses page boundaries\n");
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static_branch_disable(&hugetlb_optimize_vmemmap_key);
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return;
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}
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vmemmap_pages = (nr_pages * sizeof(struct page)) >> PAGE_SHIFT;
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/*
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* The head page is not to be freed to buddy allocator, the other tail
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* pages will map to the head page, so they can be freed.
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*
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* Could RESERVE_VMEMMAP_NR be greater than @vmemmap_pages? It is true
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* on some architectures (e.g. aarch64). See Documentation/arm64/
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* hugetlbpage.rst for more details.
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*/
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if (likely(vmemmap_pages > RESERVE_VMEMMAP_NR))
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h->optimize_vmemmap_pages = vmemmap_pages - RESERVE_VMEMMAP_NR;
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pr_info("can optimize %d vmemmap pages for %s\n",
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h->optimize_vmemmap_pages, h->name);
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}
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#ifdef CONFIG_PROC_SYSCTL
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static int hugetlb_optimize_vmemmap_handler(struct ctl_table *table, int write,
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void *buffer, size_t *length,
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loff_t *ppos)
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{
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int ret;
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enum vmemmap_optimize_mode mode;
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static DEFINE_MUTEX(sysctl_mutex);
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if (write && !capable(CAP_SYS_ADMIN))
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return -EPERM;
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mutex_lock(&sysctl_mutex);
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mode = vmemmap_optimize_mode;
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table->data = &mode;
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ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
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if (write && !ret)
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vmemmap_optimize_mode_switch(mode);
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mutex_unlock(&sysctl_mutex);
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return ret;
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}
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static struct ctl_table hugetlb_vmemmap_sysctls[] = {
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{
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.procname = "hugetlb_optimize_vmemmap",
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.maxlen = sizeof(enum vmemmap_optimize_mode),
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.mode = 0644,
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.proc_handler = hugetlb_optimize_vmemmap_handler,
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.extra1 = SYSCTL_ZERO,
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.extra2 = SYSCTL_ONE,
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},
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{ }
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};
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static __init int hugetlb_vmemmap_sysctls_init(void)
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{
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/*
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* If "memory_hotplug.memmap_on_memory" is enabled or "struct page"
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* crosses page boundaries, the vmemmap pages cannot be optimized.
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*/
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if (!mhp_memmap_on_memory() && is_power_of_2(sizeof(struct page)))
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register_sysctl_init("vm", hugetlb_vmemmap_sysctls);
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return 0;
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}
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late_initcall(hugetlb_vmemmap_sysctls_init);
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#endif /* CONFIG_PROC_SYSCTL */
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