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-rw-r--r--mm/page_idle.c232
1 files changed, 232 insertions, 0 deletions
diff --git a/mm/page_idle.c b/mm/page_idle.c
new file mode 100644
index 000000000000..d5dd79041484
--- /dev/null
+++ b/mm/page_idle.c
@@ -0,0 +1,232 @@
+#include <linux/init.h>
+#include <linux/bootmem.h>
+#include <linux/fs.h>
+#include <linux/sysfs.h>
+#include <linux/kobject.h>
+#include <linux/mm.h>
+#include <linux/mmzone.h>
+#include <linux/pagemap.h>
+#include <linux/rmap.h>
+#include <linux/mmu_notifier.h>
+#include <linux/page_ext.h>
+#include <linux/page_idle.h>
+
+#define BITMAP_CHUNK_SIZE sizeof(u64)
+#define BITMAP_CHUNK_BITS (BITMAP_CHUNK_SIZE * BITS_PER_BYTE)
+
+/*
+ * Idle page tracking only considers user memory pages, for other types of
+ * pages the idle flag is always unset and an attempt to set it is silently
+ * ignored.
+ *
+ * We treat a page as a user memory page if it is on an LRU list, because it is
+ * always safe to pass such a page to rmap_walk(), which is essential for idle
+ * page tracking. With such an indicator of user pages we can skip isolated
+ * pages, but since there are not usually many of them, it will hardly affect
+ * the overall result.
+ *
+ * This function tries to get a user memory page by pfn as described above.
+ */
+static struct page *page_idle_get_page(unsigned long pfn)
+{
+ struct page *page;
+ struct zone *zone;
+
+ if (!pfn_valid(pfn))
+ return NULL;
+
+ page = pfn_to_page(pfn);
+ if (!page || !PageLRU(page) ||
+ !get_page_unless_zero(page))
+ return NULL;
+
+ zone = page_zone(page);
+ spin_lock_irq(&zone->lru_lock);
+ if (unlikely(!PageLRU(page))) {
+ put_page(page);
+ page = NULL;
+ }
+ spin_unlock_irq(&zone->lru_lock);
+ return page;
+}
+
+static int page_idle_clear_pte_refs_one(struct page *page,
+ struct vm_area_struct *vma,
+ unsigned long addr, void *arg)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ spinlock_t *ptl;
+ pmd_t *pmd;
+ pte_t *pte;
+ bool referenced = false;
+
+ if (unlikely(PageTransHuge(page))) {
+ pmd = page_check_address_pmd(page, mm, addr,
+ PAGE_CHECK_ADDRESS_PMD_FLAG, &ptl);
+ if (pmd) {
+ referenced = pmdp_clear_young_notify(vma, addr, pmd);
+ spin_unlock(ptl);
+ }
+ } else {
+ pte = page_check_address(page, mm, addr, &ptl, 0);
+ if (pte) {
+ referenced = ptep_clear_young_notify(vma, addr, pte);
+ pte_unmap_unlock(pte, ptl);
+ }
+ }
+ if (referenced) {
+ clear_page_idle(page);
+ /*
+ * We cleared the referenced bit in a mapping to this page. To
+ * avoid interference with page reclaim, mark it young so that
+ * page_referenced() will return > 0.
+ */
+ set_page_young(page);
+ }
+ return SWAP_AGAIN;
+}
+
+static void page_idle_clear_pte_refs(struct page *page)
+{
+ /*
+ * Since rwc.arg is unused, rwc is effectively immutable, so we
+ * can make it static const to save some cycles and stack.
+ */
+ static const struct rmap_walk_control rwc = {
+ .rmap_one = page_idle_clear_pte_refs_one,
+ .anon_lock = page_lock_anon_vma_read,
+ };
+ bool need_lock;
+
+ if (!page_mapped(page) ||
+ !page_rmapping(page))
+ return;
+
+ need_lock = !PageAnon(page) || PageKsm(page);
+ if (need_lock && !trylock_page(page))
+ return;
+
+ rmap_walk(page, (struct rmap_walk_control *)&rwc);
+
+ if (need_lock)
+ unlock_page(page);
+}
+
+static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj,
+ struct bin_attribute *attr, char *buf,
+ loff_t pos, size_t count)
+{
+ u64 *out = (u64 *)buf;
+ struct page *page;
+ unsigned long pfn, end_pfn;
+ int bit;
+
+ if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
+ return -EINVAL;
+
+ pfn = pos * BITS_PER_BYTE;
+ if (pfn >= max_pfn)
+ return 0;
+
+ end_pfn = pfn + count * BITS_PER_BYTE;
+ if (end_pfn > max_pfn)
+ end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS);
+
+ for (; pfn < end_pfn; pfn++) {
+ bit = pfn % BITMAP_CHUNK_BITS;
+ if (!bit)
+ *out = 0ULL;
+ page = page_idle_get_page(pfn);
+ if (page) {
+ if (page_is_idle(page)) {
+ /*
+ * The page might have been referenced via a
+ * pte, in which case it is not idle. Clear
+ * refs and recheck.
+ */
+ page_idle_clear_pte_refs(page);
+ if (page_is_idle(page))
+ *out |= 1ULL << bit;
+ }
+ put_page(page);
+ }
+ if (bit == BITMAP_CHUNK_BITS - 1)
+ out++;
+ cond_resched();
+ }
+ return (char *)out - buf;
+}
+
+static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj,
+ struct bin_attribute *attr, char *buf,
+ loff_t pos, size_t count)
+{
+ const u64 *in = (u64 *)buf;
+ struct page *page;
+ unsigned long pfn, end_pfn;
+ int bit;
+
+ if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
+ return -EINVAL;
+
+ pfn = pos * BITS_PER_BYTE;
+ if (pfn >= max_pfn)
+ return -ENXIO;
+
+ end_pfn = pfn + count * BITS_PER_BYTE;
+ if (end_pfn > max_pfn)
+ end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS);
+
+ for (; pfn < end_pfn; pfn++) {
+ bit = pfn % BITMAP_CHUNK_BITS;
+ if ((*in >> bit) & 1) {
+ page = page_idle_get_page(pfn);
+ if (page) {
+ page_idle_clear_pte_refs(page);
+ set_page_idle(page);
+ put_page(page);
+ }
+ }
+ if (bit == BITMAP_CHUNK_BITS - 1)
+ in++;
+ cond_resched();
+ }
+ return (char *)in - buf;
+}
+
+static struct bin_attribute page_idle_bitmap_attr =
+ __BIN_ATTR(bitmap, S_IRUSR | S_IWUSR,
+ page_idle_bitmap_read, page_idle_bitmap_write, 0);
+
+static struct bin_attribute *page_idle_bin_attrs[] = {
+ &page_idle_bitmap_attr,
+ NULL,
+};
+
+static struct attribute_group page_idle_attr_group = {
+ .bin_attrs = page_idle_bin_attrs,
+ .name = "page_idle",
+};
+
+#ifndef CONFIG_64BIT
+static bool need_page_idle(void)
+{
+ return true;
+}
+struct page_ext_operations page_idle_ops = {
+ .need = need_page_idle,
+};
+#endif
+
+static int __init page_idle_init(void)
+{
+ int err;
+
+ err = sysfs_create_group(mm_kobj, &page_idle_attr_group);
+ if (err) {
+ pr_err("page_idle: register sysfs failed\n");
+ return err;
+ }
+ return 0;
+}
+subsys_initcall(page_idle_init);