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-rw-r--r--mm/page_idle.c221
1 files changed, 221 insertions, 0 deletions
diff --git a/mm/page_idle.c b/mm/page_idle.c
new file mode 100644
index 0000000000..41ea77f220
--- /dev/null
+++ b/mm/page_idle.c
@@ -0,0 +1,221 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/init.h>
+#include <linux/memblock.h>
+#include <linux/fs.h>
+#include <linux/sysfs.h>
+#include <linux/kobject.h>
+#include <linux/memory_hotplug.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>
+
+#include "internal.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 folio *page_idle_get_folio(unsigned long pfn)
+{
+ struct page *page = pfn_to_online_page(pfn);
+ struct folio *folio;
+
+ if (!page || PageTail(page))
+ return NULL;
+
+ folio = page_folio(page);
+ if (!folio_test_lru(folio) || !folio_try_get(folio))
+ return NULL;
+ if (unlikely(page_folio(page) != folio || !folio_test_lru(folio))) {
+ folio_put(folio);
+ folio = NULL;
+ }
+ return folio;
+}
+
+static bool page_idle_clear_pte_refs_one(struct folio *folio,
+ struct vm_area_struct *vma,
+ unsigned long addr, void *arg)
+{
+ DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, addr, 0);
+ bool referenced = false;
+
+ while (page_vma_mapped_walk(&pvmw)) {
+ addr = pvmw.address;
+ if (pvmw.pte) {
+ /*
+ * For PTE-mapped THP, one sub page is referenced,
+ * the whole THP is referenced.
+ */
+ if (ptep_clear_young_notify(vma, addr, pvmw.pte))
+ referenced = true;
+ } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
+ if (pmdp_clear_young_notify(vma, addr, pvmw.pmd))
+ referenced = true;
+ } else {
+ /* unexpected pmd-mapped page? */
+ WARN_ON_ONCE(1);
+ }
+ }
+
+ if (referenced) {
+ folio_clear_idle(folio);
+ /*
+ * We cleared the referenced bit in a mapping to this page. To
+ * avoid interference with page reclaim, mark it young so that
+ * folio_referenced() will return > 0.
+ */
+ folio_set_young(folio);
+ }
+ return true;
+}
+
+static void page_idle_clear_pte_refs(struct folio *folio)
+{
+ /*
+ * Since rwc.try_lock is unused, rwc is effectively immutable, so we
+ * can make it static to save some cycles and stack.
+ */
+ static struct rmap_walk_control rwc = {
+ .rmap_one = page_idle_clear_pte_refs_one,
+ .anon_lock = folio_lock_anon_vma_read,
+ };
+ bool need_lock;
+
+ if (!folio_mapped(folio) || !folio_raw_mapping(folio))
+ return;
+
+ need_lock = !folio_test_anon(folio) || folio_test_ksm(folio);
+ if (need_lock && !folio_trylock(folio))
+ return;
+
+ rmap_walk(folio, &rwc);
+
+ if (need_lock)
+ folio_unlock(folio);
+}
+
+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 folio *folio;
+ 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 = max_pfn;
+
+ for (; pfn < end_pfn; pfn++) {
+ bit = pfn % BITMAP_CHUNK_BITS;
+ if (!bit)
+ *out = 0ULL;
+ folio = page_idle_get_folio(pfn);
+ if (folio) {
+ if (folio_test_idle(folio)) {
+ /*
+ * 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(folio);
+ if (folio_test_idle(folio))
+ *out |= 1ULL << bit;
+ }
+ folio_put(folio);
+ }
+ 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 folio *folio;
+ 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 = max_pfn;
+
+ for (; pfn < end_pfn; pfn++) {
+ bit = pfn % BITMAP_CHUNK_BITS;
+ if ((*in >> bit) & 1) {
+ folio = page_idle_get_folio(pfn);
+ if (folio) {
+ page_idle_clear_pte_refs(folio);
+ folio_set_idle(folio);
+ folio_put(folio);
+ }
+ }
+ if (bit == BITMAP_CHUNK_BITS - 1)
+ in++;
+ cond_resched();
+ }
+ return (char *)in - buf;
+}
+
+static struct bin_attribute page_idle_bitmap_attr =
+ __BIN_ATTR(bitmap, 0600,
+ page_idle_bitmap_read, page_idle_bitmap_write, 0);
+
+static struct bin_attribute *page_idle_bin_attrs[] = {
+ &page_idle_bitmap_attr,
+ NULL,
+};
+
+static const struct attribute_group page_idle_attr_group = {
+ .bin_attrs = page_idle_bin_attrs,
+ .name = "page_idle",
+};
+
+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);