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}
122