diff --git a/Documentation/vm/00-INDEX b/Documentation/vm/00-INDEX
index 081c497..6a5e2a1 100644
--- a/Documentation/vm/00-INDEX
+++ b/Documentation/vm/00-INDEX
@@ -14,6 +14,8 @@
 	- a brief summary of hugetlbpage support in the Linux kernel.
 hwpoison.txt
 	- explains what hwpoison is
+idle_page_tracking.txt
+	- description of the idle page tracking feature.
 ksm.txt
 	- how to use the Kernel Samepage Merging feature.
 numa
diff --git a/Documentation/vm/idle_page_tracking.txt b/Documentation/vm/idle_page_tracking.txt
new file mode 100644
index 0000000..85dcc3b
--- /dev/null
+++ b/Documentation/vm/idle_page_tracking.txt
@@ -0,0 +1,98 @@
+MOTIVATION
+
+The idle page tracking feature allows to track which memory pages are being
+accessed by a workload and which are idle. This information can be useful for
+estimating the workload's working set size, which, in turn, can be taken into
+account when configuring the workload parameters, setting memory cgroup limits,
+or deciding where to place the workload within a compute cluster.
+
+It is enabled by CONFIG_IDLE_PAGE_TRACKING=y.
+
+USER API
+
+The idle page tracking API is located at /sys/kernel/mm/page_idle. Currently,
+it consists of the only read-write file, /sys/kernel/mm/page_idle/bitmap.
+
+The file implements a bitmap where each bit corresponds to a memory page. The
+bitmap is represented by an array of 8-byte integers, and the page at PFN #i is
+mapped to bit #i%64 of array element #i/64, byte order is native. When a bit is
+set, the corresponding page is idle.
+
+A page is considered idle if it has not been accessed since it was marked idle
+(for more details on what "accessed" actually means see the IMPLEMENTATION
+DETAILS section). To mark a page idle one has to set the bit corresponding to
+the page by writing to the file. A value written to the file is OR-ed with the
+current bitmap value.
+
+Only accesses to user memory pages are tracked. These are pages mapped to a
+process address space, page cache and buffer pages, swap cache pages. For other
+page types (e.g. SLAB pages) an attempt to mark a page idle is silently ignored,
+and hence such pages are never reported idle.
+
+For huge pages the idle flag is set only on the head page, so one has to read
+/proc/kpageflags in order to correctly count idle huge pages.
+
+Reading from or writing to /sys/kernel/mm/page_idle/bitmap will return
+-EINVAL if you are not starting the read/write on an 8-byte boundary, or
+if the size of the read/write is not a multiple of 8 bytes. Writing to
+this file beyond max PFN will return -ENXIO.
+
+That said, in order to estimate the amount of pages that are not used by a
+workload one should:
+
+ 1. Mark all the workload's pages as idle by setting corresponding bits in
+    /sys/kernel/mm/page_idle/bitmap. The pages can be found by reading
+    /proc/pid/pagemap if the workload is represented by a process, or by
+    filtering out alien pages using /proc/kpagecgroup in case the workload is
+    placed in a memory cgroup.
+
+ 2. Wait until the workload accesses its working set.
+
+ 3. Read /sys/kernel/mm/page_idle/bitmap and count the number of bits set. If
+    one wants to ignore certain types of pages, e.g. mlocked pages since they
+    are not reclaimable, he or she can filter them out using /proc/kpageflags.
+
+See Documentation/vm/pagemap.txt for more information about /proc/pid/pagemap,
+/proc/kpageflags, and /proc/kpagecgroup.
+
+IMPLEMENTATION DETAILS
+
+The kernel internally keeps track of accesses to user memory pages in order to
+reclaim unreferenced pages first on memory shortage conditions. A page is
+considered referenced if it has been recently accessed via a process address
+space, in which case one or more PTEs it is mapped to will have the Accessed bit
+set, or marked accessed explicitly by the kernel (see mark_page_accessed()). The
+latter happens when:
+
+ - a userspace process reads or writes a page using a system call (e.g. read(2)
+   or write(2))
+
+ - a page that is used for storing filesystem buffers is read or written,
+   because a process needs filesystem metadata stored in it (e.g. lists a
+   directory tree)
+
+ - a page is accessed by a device driver using get_user_pages()
+
+When a dirty page is written to swap or disk as a result of memory reclaim or
+exceeding the dirty memory limit, it is not marked referenced.
+
+The idle memory tracking feature adds a new page flag, the Idle flag. This flag
+is set manually, by writing to /sys/kernel/mm/page_idle/bitmap (see the USER API
+section), and cleared automatically whenever a page is referenced as defined
+above.
+
+When a page is marked idle, the Accessed bit must be cleared in all PTEs it is
+mapped to, otherwise we will not be able to detect accesses to the page coming
+from a process address space. To avoid interference with the reclaimer, which,
+as noted above, uses the Accessed bit to promote actively referenced pages, one
+more page flag is introduced, the Young flag. When the PTE Accessed bit is
+cleared as a result of setting or updating a page's Idle flag, the Young flag
+is set on the page. The reclaimer treats the Young flag as an extra PTE
+Accessed bit and therefore will consider such a page as referenced.
+
+Since the idle memory tracking feature is based on the memory reclaimer logic,
+it only works with pages that are on an LRU list, other pages are silently
+ignored. That means it will ignore a user memory page if it is isolated, but
+since there are usually not many of them, it should not affect the overall
+result noticeably. In order not to stall scanning of the idle page bitmap,
+locked pages may be skipped too.
diff --git a/fs/proc/page.c b/fs/proc/page.c
index 70d2324..c2d29edc 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -10,12 +10,15 @@
 #include <linux/seq_file.h>
 #include <linux/hugetlb.h>
 #include <linux/memcontrol.h>
+#include <linux/mmu_notifier.h>
+#include <linux/page_idle.h>
 #include <linux/kernel-page-flags.h>
 #include <asm/uaccess.h>
 #include "internal.h"
 
 #define KPMSIZE sizeof(u64)
 #define KPMMASK (KPMSIZE - 1)
+#define KPMBITS (KPMSIZE * BITS_PER_BYTE)
 
 /* /proc/kpagecount - an array exposing page counts
  *
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 41f1a50..e2d46ad 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -13,6 +13,7 @@
 #include <linux/swap.h>
 #include <linux/swapops.h>
 #include <linux/mmu_notifier.h>
+#include <linux/page_idle.h>
 
 #include <asm/elf.h>
 #include <asm/uaccess.h>
@@ -459,7 +460,7 @@
 
 	mss->resident += size;
 	/* Accumulate the size in pages that have been accessed. */
-	if (young || PageReferenced(page))
+	if (young || page_is_young(page) || PageReferenced(page))
 		mss->referenced += size;
 	mapcount = page_mapcount(page);
 	if (mapcount >= 2) {
@@ -807,6 +808,7 @@
 
 		/* Clear accessed and referenced bits. */
 		pmdp_test_and_clear_young(vma, addr, pmd);
+		test_and_clear_page_young(page);
 		ClearPageReferenced(page);
 out:
 		spin_unlock(ptl);
@@ -834,6 +836,7 @@
 
 		/* Clear accessed and referenced bits. */
 		ptep_test_and_clear_young(vma, addr, pte);
+		test_and_clear_page_young(page);
 		ClearPageReferenced(page);
 	}
 	pte_unmap_unlock(pte - 1, ptl);
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index a5b1713..a1a210d 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -471,6 +471,8 @@
 
 #define ptep_clear_flush_young_notify ptep_clear_flush_young
 #define pmdp_clear_flush_young_notify pmdp_clear_flush_young
+#define ptep_clear_young_notify ptep_test_and_clear_young
+#define pmdp_clear_young_notify pmdp_test_and_clear_young
 #define	ptep_clear_flush_notify ptep_clear_flush
 #define pmdp_huge_clear_flush_notify pmdp_huge_clear_flush
 #define pmdp_huge_get_and_clear_notify pmdp_huge_get_and_clear
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 41c9384..416509e 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -109,6 +109,10 @@
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	PG_compound_lock,
 #endif
+#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
+	PG_young,
+	PG_idle,
+#endif
 	__NR_PAGEFLAGS,
 
 	/* Filesystems */
@@ -289,6 +293,13 @@
 #define __PG_HWPOISON 0
 #endif
 
+#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
+TESTPAGEFLAG(Young, young)
+SETPAGEFLAG(Young, young)
+TESTCLEARFLAG(Young, young)
+PAGEFLAG(Idle, idle)
+#endif
+
 /*
  * On an anonymous page mapped into a user virtual memory area,
  * page->mapping points to its anon_vma, not to a struct address_space;
diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
index c42981c..17f118a 100644
--- a/include/linux/page_ext.h
+++ b/include/linux/page_ext.h
@@ -26,6 +26,10 @@
 	PAGE_EXT_DEBUG_POISON,		/* Page is poisoned */
 	PAGE_EXT_DEBUG_GUARD,
 	PAGE_EXT_OWNER,
+#if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
+	PAGE_EXT_YOUNG,
+	PAGE_EXT_IDLE,
+#endif
 };
 
 /*
diff --git a/include/linux/page_idle.h b/include/linux/page_idle.h
new file mode 100644
index 0000000..bf268fa
--- /dev/null
+++ b/include/linux/page_idle.h
@@ -0,0 +1,110 @@
+#ifndef _LINUX_MM_PAGE_IDLE_H
+#define _LINUX_MM_PAGE_IDLE_H
+
+#include <linux/bitops.h>
+#include <linux/page-flags.h>
+#include <linux/page_ext.h>
+
+#ifdef CONFIG_IDLE_PAGE_TRACKING
+
+#ifdef CONFIG_64BIT
+static inline bool page_is_young(struct page *page)
+{
+	return PageYoung(page);
+}
+
+static inline void set_page_young(struct page *page)
+{
+	SetPageYoung(page);
+}
+
+static inline bool test_and_clear_page_young(struct page *page)
+{
+	return TestClearPageYoung(page);
+}
+
+static inline bool page_is_idle(struct page *page)
+{
+	return PageIdle(page);
+}
+
+static inline void set_page_idle(struct page *page)
+{
+	SetPageIdle(page);
+}
+
+static inline void clear_page_idle(struct page *page)
+{
+	ClearPageIdle(page);
+}
+#else /* !CONFIG_64BIT */
+/*
+ * If there is not enough space to store Idle and Young bits in page flags, use
+ * page ext flags instead.
+ */
+extern struct page_ext_operations page_idle_ops;
+
+static inline bool page_is_young(struct page *page)
+{
+	return test_bit(PAGE_EXT_YOUNG, &lookup_page_ext(page)->flags);
+}
+
+static inline void set_page_young(struct page *page)
+{
+	set_bit(PAGE_EXT_YOUNG, &lookup_page_ext(page)->flags);
+}
+
+static inline bool test_and_clear_page_young(struct page *page)
+{
+	return test_and_clear_bit(PAGE_EXT_YOUNG,
+				  &lookup_page_ext(page)->flags);
+}
+
+static inline bool page_is_idle(struct page *page)
+{
+	return test_bit(PAGE_EXT_IDLE, &lookup_page_ext(page)->flags);
+}
+
+static inline void set_page_idle(struct page *page)
+{
+	set_bit(PAGE_EXT_IDLE, &lookup_page_ext(page)->flags);
+}
+
+static inline void clear_page_idle(struct page *page)
+{
+	clear_bit(PAGE_EXT_IDLE, &lookup_page_ext(page)->flags);
+}
+#endif /* CONFIG_64BIT */
+
+#else /* !CONFIG_IDLE_PAGE_TRACKING */
+
+static inline bool page_is_young(struct page *page)
+{
+	return false;
+}
+
+static inline void set_page_young(struct page *page)
+{
+}
+
+static inline bool test_and_clear_page_young(struct page *page)
+{
+	return false;
+}
+
+static inline bool page_is_idle(struct page *page)
+{
+	return false;
+}
+
+static inline void set_page_idle(struct page *page)
+{
+}
+
+static inline void clear_page_idle(struct page *page)
+{
+}
+
+#endif /* CONFIG_IDLE_PAGE_TRACKING */
+
+#endif /* _LINUX_MM_PAGE_IDLE_H */
diff --git a/mm/Kconfig b/mm/Kconfig
index 3a4070f..6413d02 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -649,6 +649,18 @@
 	  processes running early in the lifetime of the systemm until kswapd
 	  finishes the initialisation.
 
+config IDLE_PAGE_TRACKING
+	bool "Enable idle page tracking"
+	depends on SYSFS && MMU
+	select PAGE_EXTENSION if !64BIT
+	help
+	  This feature allows to estimate the amount of user pages that have
+	  not been touched during a given period of time. This information can
+	  be useful to tune memory cgroup limits and/or for job placement
+	  within a compute cluster.
+
+	  See Documentation/vm/idle_page_tracking.txt for more details.
+
 config ZONE_DEVICE
 	bool "Device memory (pmem, etc...) hotplug support" if EXPERT
 	default !ZONE_DMA
diff --git a/mm/Makefile b/mm/Makefile
index b424d5e..56f8eed 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -79,3 +79,4 @@
 obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o
 obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o
 obj-$(CONFIG_USERFAULTFD) += userfaultfd.o
+obj-$(CONFIG_IDLE_PAGE_TRACKING) += page_idle.o
diff --git a/mm/debug.c b/mm/debug.c
index 76089dd..6c1b3ea 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -48,6 +48,10 @@
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	{1UL << PG_compound_lock,	"compound_lock"	},
 #endif
+#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
+	{1UL << PG_young,		"young"		},
+	{1UL << PG_idle,		"idle"		},
+#endif
 };
 
 static void dump_flags(unsigned long flags,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b16279c..4b06b8d 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -25,6 +25,7 @@
 #include <linux/migrate.h>
 #include <linux/hashtable.h>
 #include <linux/userfaultfd_k.h>
+#include <linux/page_idle.h>
 
 #include <asm/tlb.h>
 #include <asm/pgalloc.h>
@@ -1757,6 +1758,11 @@
 		/* clear PageTail before overwriting first_page */
 		smp_wmb();
 
+		if (page_is_young(page))
+			set_page_young(page_tail);
+		if (page_is_idle(page))
+			set_page_idle(page_tail);
+
 		/*
 		 * __split_huge_page_splitting() already set the
 		 * splitting bit in all pmd that could map this
@@ -2262,7 +2268,8 @@
 		VM_BUG_ON_PAGE(PageLRU(page), page);
 
 		/* If there is no mapped pte young don't collapse the page */
-		if (pte_young(pteval) || PageReferenced(page) ||
+		if (pte_young(pteval) ||
+		    page_is_young(page) || PageReferenced(page) ||
 		    mmu_notifier_test_young(vma->vm_mm, address))
 			referenced = true;
 	}
@@ -2693,7 +2700,8 @@
 		 */
 		if (page_count(page) != 1 + !!PageSwapCache(page))
 			goto out_unmap;
-		if (pte_young(pteval) || PageReferenced(page) ||
+		if (pte_young(pteval) ||
+		    page_is_young(page) || PageReferenced(page) ||
 		    mmu_notifier_test_young(vma->vm_mm, address))
 			referenced = true;
 	}
diff --git a/mm/migrate.c b/mm/migrate.c
index 02ce25d..c3cb566 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -37,6 +37,7 @@
 #include <linux/gfp.h>
 #include <linux/balloon_compaction.h>
 #include <linux/mmu_notifier.h>
+#include <linux/page_idle.h>
 
 #include <asm/tlbflush.h>
 
@@ -524,6 +525,11 @@
 			__set_page_dirty_nobuffers(newpage);
  	}
 
+	if (page_is_young(page))
+		set_page_young(newpage);
+	if (page_is_idle(page))
+		set_page_idle(newpage);
+
 	/*
 	 * Copy NUMA information to the new page, to prevent over-eager
 	 * future migrations of this same page.
diff --git a/mm/page_ext.c b/mm/page_ext.c
index d86fd2f..292ca7b 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -6,6 +6,7 @@
 #include <linux/vmalloc.h>
 #include <linux/kmemleak.h>
 #include <linux/page_owner.h>
+#include <linux/page_idle.h>
 
 /*
  * struct page extension
@@ -59,6 +60,9 @@
 #ifdef CONFIG_PAGE_OWNER
 	&page_owner_ops,
 #endif
+#if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
+	&page_idle_ops,
+#endif
 };
 
 static unsigned long total_usage;
diff --git a/mm/page_idle.c b/mm/page_idle.c
new file mode 100644
index 0000000..d5dd790
--- /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);
diff --git a/mm/rmap.c b/mm/rmap.c
index 0db38e7..f5b5c1f 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -59,6 +59,7 @@
 #include <linux/migrate.h>
 #include <linux/hugetlb.h>
 #include <linux/backing-dev.h>
+#include <linux/page_idle.h>
 
 #include <asm/tlbflush.h>
 
@@ -886,6 +887,11 @@
 		pte_unmap_unlock(pte, ptl);
 	}
 
+	if (referenced)
+		clear_page_idle(page);
+	if (test_and_clear_page_young(page))
+		referenced++;
+
 	if (referenced) {
 		pra->referenced++;
 		pra->vm_flags |= vma->vm_flags;
diff --git a/mm/swap.c b/mm/swap.c
index a3a0a2f..983f692 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -32,6 +32,7 @@
 #include <linux/gfp.h>
 #include <linux/uio.h>
 #include <linux/hugetlb.h>
+#include <linux/page_idle.h>
 
 #include "internal.h"
 
@@ -622,6 +623,8 @@
 	} else if (!PageReferenced(page)) {
 		SetPageReferenced(page);
 	}
+	if (page_is_idle(page))
+		clear_page_idle(page);
 }
 EXPORT_SYMBOL(mark_page_accessed);