diff options
Diffstat (limited to 'mm/page_idle.c')
| -rw-r--r-- | mm/page_idle.c | 221 |
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); |