1 #include <linux/init.h>
2 #include <linux/bootmem.h>
4 #include <linux/sysfs.h>
5 #include <linux/kobject.h>
7 #include <linux/mmzone.h>
8 #include <linux/pagemap.h>
9 #include <linux/rmap.h>
10 #include <linux/mmu_notifier.h>
11 #include <linux/page_ext.h>
12 #include <linux/page_idle.h>
14 #define BITMAP_CHUNK_SIZE sizeof(u64)
15 #define BITMAP_CHUNK_BITS (BITMAP_CHUNK_SIZE * BITS_PER_BYTE)
18 * Idle page tracking only considers user memory pages, for other types of
19 * pages the idle flag is always unset and an attempt to set it is silently
22 * We treat a page as a user memory page if it is on an LRU list, because it is
23 * always safe to pass such a page to rmap_walk(), which is essential for idle
24 * page tracking. With such an indicator of user pages we can skip isolated
25 * pages, but since there are not usually many of them, it will hardly affect
28 * This function tries to get a user memory page by pfn as described above.
30 static struct page *page_idle_get_page(unsigned long pfn)
38 page = pfn_to_page(pfn);
39 if (!page || !PageLRU(page) ||
40 !get_page_unless_zero(page))
43 zone = page_zone(page);
44 spin_lock_irq(&zone->lru_lock);
45 if (unlikely(!PageLRU(page))) {
49 spin_unlock_irq(&zone->lru_lock);
53 static int page_idle_clear_pte_refs_one(struct page *page,
54 struct vm_area_struct *vma,
55 unsigned long addr, void *arg)
57 struct mm_struct *mm = vma->vm_mm;
61 bool referenced = false;
63 if (unlikely(PageTransHuge(page))) {
64 pmd = page_check_address_pmd(page, mm, addr,
65 PAGE_CHECK_ADDRESS_PMD_FLAG, &ptl);
67 referenced = pmdp_clear_young_notify(vma, addr, pmd);
71 pte = page_check_address(page, mm, addr, &ptl, 0);
73 referenced = ptep_clear_young_notify(vma, addr, pte);
74 pte_unmap_unlock(pte, ptl);
78 clear_page_idle(page);
80 * We cleared the referenced bit in a mapping to this page. To
81 * avoid interference with page reclaim, mark it young so that
82 * page_referenced() will return > 0.
89 static void page_idle_clear_pte_refs(struct page *page)
92 * Since rwc.arg is unused, rwc is effectively immutable, so we
93 * can make it static const to save some cycles and stack.
95 static const struct rmap_walk_control rwc = {
96 .rmap_one = page_idle_clear_pte_refs_one,
97 .anon_lock = page_lock_anon_vma_read,
101 if (!page_mapped(page) ||
102 !page_rmapping(page))
105 need_lock = !PageAnon(page) || PageKsm(page);
106 if (need_lock && !trylock_page(page))
109 rmap_walk(page, (struct rmap_walk_control *)&rwc);
115 static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj,
116 struct bin_attribute *attr, char *buf,
117 loff_t pos, size_t count)
119 u64 *out = (u64 *)buf;
121 unsigned long pfn, end_pfn;
124 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
127 pfn = pos * BITS_PER_BYTE;
131 end_pfn = pfn + count * BITS_PER_BYTE;
132 if (end_pfn > max_pfn)
133 end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS);
135 for (; pfn < end_pfn; pfn++) {
136 bit = pfn % BITMAP_CHUNK_BITS;
139 page = page_idle_get_page(pfn);
141 if (page_is_idle(page)) {
143 * The page might have been referenced via a
144 * pte, in which case it is not idle. Clear
147 page_idle_clear_pte_refs(page);
148 if (page_is_idle(page))
153 if (bit == BITMAP_CHUNK_BITS - 1)
157 return (char *)out - buf;
160 static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj,
161 struct bin_attribute *attr, char *buf,
162 loff_t pos, size_t count)
164 const u64 *in = (u64 *)buf;
166 unsigned long pfn, end_pfn;
169 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
172 pfn = pos * BITS_PER_BYTE;
176 end_pfn = pfn + count * BITS_PER_BYTE;
177 if (end_pfn > max_pfn)
178 end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS);
180 for (; pfn < end_pfn; pfn++) {
181 bit = pfn % BITMAP_CHUNK_BITS;
182 if ((*in >> bit) & 1) {
183 page = page_idle_get_page(pfn);
185 page_idle_clear_pte_refs(page);
190 if (bit == BITMAP_CHUNK_BITS - 1)
194 return (char *)in - buf;
197 static struct bin_attribute page_idle_bitmap_attr =
198 __BIN_ATTR(bitmap, S_IRUSR | S_IWUSR,
199 page_idle_bitmap_read, page_idle_bitmap_write, 0);
201 static struct bin_attribute *page_idle_bin_attrs[] = {
202 &page_idle_bitmap_attr,
206 static struct attribute_group page_idle_attr_group = {
207 .bin_attrs = page_idle_bin_attrs,
212 static bool need_page_idle(void)
216 struct page_ext_operations page_idle_ops = {
217 .need = need_page_idle,
221 static int __init page_idle_init(void)
225 err = sysfs_create_group(mm_kobj, &page_idle_attr_group);
227 pr_err("page_idle: register sysfs failed\n");
232 subsys_initcall(page_idle_init);