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 */
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
40 void 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
54 void 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
73 int 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
114 int 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
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