1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Common Primitives for Data Access Monitoring
  4 *
  5 * Author: SeongJae Park <sj@kernel.org>
  6 */
  7
  8#include <linux/mmu_notifier.h>
  9#include <linux/page_idle.h>
 10#include <linux/pagemap.h>
 11#include <linux/rmap.h>
 12
 13#include "ops-common.h"
 14
 15/*
 16 * Get an online page for a pfn if it's in the LRU list.  Otherwise, returns
 17 * NULL.
 18 *
 19 * The body of this function is stolen from the 'page_idle_get_folio()'.  We
 20 * steal rather than reuse it because the code is quite simple.
 21 */
 22struct folio *damon_get_folio(unsigned long pfn)
 23{
 24	struct page *page = pfn_to_online_page(pfn);
 25	struct folio *folio;
 26
 27	if (!page || PageTail(page))
 28		return NULL;
 29
 30	folio = page_folio(page);
 31	if (!folio_test_lru(folio) || !folio_try_get(folio))
 32		return NULL;
 33	if (unlikely(page_folio(page) != folio || !folio_test_lru(folio))) {
 34		folio_put(folio);
 35		folio = NULL;
 36	}
 37	return folio;
 38}
 39
 40void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr)
 41{
 42	struct folio *folio = damon_get_folio(pte_pfn(ptep_get(pte)));
 43
 44	if (!folio)
 45		return;
 46
 47	if (ptep_clear_young_notify(vma, addr, pte))
 48		folio_set_young(folio);
 49
 50	folio_set_idle(folio);
 51	folio_put(folio);
 52}
 53
 54void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr)
 55{
 56#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 57	struct folio *folio = damon_get_folio(pmd_pfn(pmdp_get(pmd)));
 58
 59	if (!folio)
 60		return;
 61
 62	if (pmdp_clear_young_notify(vma, addr, pmd))
 63		folio_set_young(folio);
 64
 65	folio_set_idle(folio);
 66	folio_put(folio);
 67#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 68}
 69
 70#define DAMON_MAX_SUBSCORE	(100)
 71#define DAMON_MAX_AGE_IN_LOG	(32)
 72
 73int damon_hot_score(struct damon_ctx *c, struct damon_region *r,
 74			struct damos *s)
 75{
 76	int freq_subscore;
 77	unsigned int age_in_sec;
 78	int age_in_log, age_subscore;
 79	unsigned int freq_weight = s->quota.weight_nr_accesses;
 80	unsigned int age_weight = s->quota.weight_age;
 81	int hotness;
 82
 83	freq_subscore = r->nr_accesses * DAMON_MAX_SUBSCORE /
 84		damon_max_nr_accesses(&c->attrs);
 85
 86	age_in_sec = (unsigned long)r->age * c->attrs.aggr_interval / 1000000;
 87	for (age_in_log = 0; age_in_log < DAMON_MAX_AGE_IN_LOG && age_in_sec;
 88			age_in_log++, age_in_sec >>= 1)
 89		;
 90
 91	/* If frequency is 0, higher age means it's colder */
 92	if (freq_subscore == 0)
 93		age_in_log *= -1;
 94
 95	/*
 96	 * Now age_in_log is in [-DAMON_MAX_AGE_IN_LOG, DAMON_MAX_AGE_IN_LOG].
 97	 * Scale it to be in [0, 100] and set it as age subscore.
 98	 */
 99	age_in_log += DAMON_MAX_AGE_IN_LOG;
100	age_subscore = age_in_log * DAMON_MAX_SUBSCORE /
101		DAMON_MAX_AGE_IN_LOG / 2;
102
103	hotness = (freq_weight * freq_subscore + age_weight * age_subscore);
104	if (freq_weight + age_weight)
105		hotness /= freq_weight + age_weight;
106	/*
107	 * Transform it to fit in [0, DAMOS_MAX_SCORE]
108	 */
109	hotness = hotness * DAMOS_MAX_SCORE / DAMON_MAX_SUBSCORE;
110
111	return hotness;
112}
113
114int damon_cold_score(struct damon_ctx *c, struct damon_region *r,
115			struct damos *s)
116{
117	int hotness = damon_hot_score(c, r, s);
118
119	/* Return coldness of the region */
120	return DAMOS_MAX_SCORE - hotness;
121}