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 */
damon_get_folio(unsigned long pfn)22 struct 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
damon_ptep_mkold(pte_t * pte,struct mm_struct * mm,unsigned long addr)40 void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr)
41 {
42 bool referenced = false;
43 struct folio *folio = damon_get_folio(pte_pfn(*pte));
44
45 if (!folio)
46 return;
47
48 if (pte_young(*pte)) {
49 referenced = true;
50 *pte = pte_mkold(*pte);
51 }
52
53 #ifdef CONFIG_MMU_NOTIFIER
54 if (mmu_notifier_clear_young(mm, addr, addr + PAGE_SIZE))
55 referenced = true;
56 #endif /* CONFIG_MMU_NOTIFIER */
57
58 if (referenced)
59 folio_set_young(folio);
60
61 folio_set_idle(folio);
62 folio_put(folio);
63 }
64
damon_pmdp_mkold(pmd_t * pmd,struct mm_struct * mm,unsigned long addr)65 void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, unsigned long addr)
66 {
67 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
68 bool referenced = false;
69 struct folio *folio = damon_get_folio(pmd_pfn(*pmd));
70
71 if (!folio)
72 return;
73
74 if (pmd_young(*pmd)) {
75 referenced = true;
76 *pmd = pmd_mkold(*pmd);
77 }
78
79 #ifdef CONFIG_MMU_NOTIFIER
80 if (mmu_notifier_clear_young(mm, addr, addr + HPAGE_PMD_SIZE))
81 referenced = true;
82 #endif /* CONFIG_MMU_NOTIFIER */
83
84 if (referenced)
85 folio_set_young(folio);
86
87 folio_set_idle(folio);
88 folio_put(folio);
89 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
90 }
91
92 #define DAMON_MAX_SUBSCORE (100)
93 #define DAMON_MAX_AGE_IN_LOG (32)
94
damon_hot_score(struct damon_ctx * c,struct damon_region * r,struct damos * s)95 int damon_hot_score(struct damon_ctx *c, struct damon_region *r,
96 struct damos *s)
97 {
98 unsigned int max_nr_accesses;
99 int freq_subscore;
100 unsigned int age_in_sec;
101 int age_in_log, age_subscore;
102 unsigned int freq_weight = s->quota.weight_nr_accesses;
103 unsigned int age_weight = s->quota.weight_age;
104 int hotness;
105
106 max_nr_accesses = c->attrs.aggr_interval / c->attrs.sample_interval;
107 freq_subscore = r->nr_accesses * DAMON_MAX_SUBSCORE / max_nr_accesses;
108
109 age_in_sec = (unsigned long)r->age * c->attrs.aggr_interval / 1000000;
110 for (age_in_log = 0; age_in_log < DAMON_MAX_AGE_IN_LOG && age_in_sec;
111 age_in_log++, age_in_sec >>= 1)
112 ;
113
114 /* If frequency is 0, higher age means it's colder */
115 if (freq_subscore == 0)
116 age_in_log *= -1;
117
118 /*
119 * Now age_in_log is in [-DAMON_MAX_AGE_IN_LOG, DAMON_MAX_AGE_IN_LOG].
120 * Scale it to be in [0, 100] and set it as age subscore.
121 */
122 age_in_log += DAMON_MAX_AGE_IN_LOG;
123 age_subscore = age_in_log * DAMON_MAX_SUBSCORE /
124 DAMON_MAX_AGE_IN_LOG / 2;
125
126 hotness = (freq_weight * freq_subscore + age_weight * age_subscore);
127 if (freq_weight + age_weight)
128 hotness /= freq_weight + age_weight;
129 /*
130 * Transform it to fit in [0, DAMOS_MAX_SCORE]
131 */
132 hotness = hotness * DAMOS_MAX_SCORE / DAMON_MAX_SUBSCORE;
133
134 return hotness;
135 }
136
damon_cold_score(struct damon_ctx * c,struct damon_region * r,struct damos * s)137 int damon_cold_score(struct damon_ctx *c, struct damon_region *r,
138 struct damos *s)
139 {
140 int hotness = damon_hot_score(c, r, s);
141
142 /* Return coldness of the region */
143 return DAMOS_MAX_SCORE - hotness;
144 }
145