1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Common Code 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 #include <linux/swap.h>
13 #include <linux/swapops.h>
14
15 #include "ops-common.h"
16
17 /*
18 * Get an online page for a pfn if it's in the LRU list. Otherwise, returns
19 * NULL.
20 *
21 * The body of this function is stolen from the 'page_idle_get_folio()'. We
22 * steal rather than reuse it because the code is quite simple.
23 */
damon_get_folio(unsigned long pfn)24 struct folio *damon_get_folio(unsigned long pfn)
25 {
26 struct page *page = pfn_to_online_page(pfn);
27 struct folio *folio;
28
29 if (!page)
30 return NULL;
31
32 folio = page_folio(page);
33 if (!folio_test_lru(folio) || !folio_try_get(folio))
34 return NULL;
35 if (unlikely(page_folio(page) != folio || !folio_test_lru(folio))) {
36 folio_put(folio);
37 folio = NULL;
38 }
39 return folio;
40 }
41
damon_ptep_mkold(pte_t * pte,struct vm_area_struct * vma,unsigned long addr)42 void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr)
43 {
44 pte_t pteval = ptep_get(pte);
45 struct folio *folio;
46 bool young = false;
47 unsigned long pfn;
48
49 if (likely(pte_present(pteval)))
50 pfn = pte_pfn(pteval);
51 else
52 pfn = swp_offset_pfn(pte_to_swp_entry(pteval));
53
54 folio = damon_get_folio(pfn);
55 if (!folio)
56 return;
57
58 /*
59 * PFN swap PTEs, such as device-exclusive ones, that actually map pages
60 * are "old" from a CPU perspective. The MMU notifier takes care of any
61 * device aspects.
62 */
63 if (likely(pte_present(pteval)))
64 young |= ptep_test_and_clear_young(vma, addr, pte);
65 young |= mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE);
66 if (young)
67 folio_set_young(folio);
68
69 folio_set_idle(folio);
70 folio_put(folio);
71 }
72
damon_pmdp_mkold(pmd_t * pmd,struct vm_area_struct * vma,unsigned long addr)73 void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr)
74 {
75 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
76 struct folio *folio = damon_get_folio(pmd_pfn(pmdp_get(pmd)));
77
78 if (!folio)
79 return;
80
81 if (pmdp_clear_young_notify(vma, addr, pmd))
82 folio_set_young(folio);
83
84 folio_set_idle(folio);
85 folio_put(folio);
86 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
87 }
88
89 #define DAMON_MAX_SUBSCORE (100)
90 #define DAMON_MAX_AGE_IN_LOG (32)
91
damon_hot_score(struct damon_ctx * c,struct damon_region * r,struct damos * s)92 int damon_hot_score(struct damon_ctx *c, struct damon_region *r,
93 struct damos *s)
94 {
95 int freq_subscore;
96 unsigned int age_in_sec;
97 int age_in_log, age_subscore;
98 unsigned int freq_weight = s->quota.weight_nr_accesses;
99 unsigned int age_weight = s->quota.weight_age;
100 int hotness;
101
102 freq_subscore = r->nr_accesses * DAMON_MAX_SUBSCORE /
103 damon_max_nr_accesses(&c->attrs);
104
105 age_in_sec = (unsigned long)r->age * c->attrs.aggr_interval / 1000000;
106 for (age_in_log = 0; age_in_log < DAMON_MAX_AGE_IN_LOG && age_in_sec;
107 age_in_log++, age_in_sec >>= 1)
108 ;
109
110 /* If frequency is 0, higher age means it's colder */
111 if (freq_subscore == 0)
112 age_in_log *= -1;
113
114 /*
115 * Now age_in_log is in [-DAMON_MAX_AGE_IN_LOG, DAMON_MAX_AGE_IN_LOG].
116 * Scale it to be in [0, 100] and set it as age subscore.
117 */
118 age_in_log += DAMON_MAX_AGE_IN_LOG;
119 age_subscore = age_in_log * DAMON_MAX_SUBSCORE /
120 DAMON_MAX_AGE_IN_LOG / 2;
121
122 hotness = (freq_weight * freq_subscore + age_weight * age_subscore);
123 if (freq_weight + age_weight)
124 hotness /= freq_weight + age_weight;
125 /*
126 * Transform it to fit in [0, DAMOS_MAX_SCORE]
127 */
128 hotness = hotness * DAMOS_MAX_SCORE / DAMON_MAX_SUBSCORE;
129
130 return hotness;
131 }
132
damon_cold_score(struct damon_ctx * c,struct damon_region * r,struct damos * s)133 int damon_cold_score(struct damon_ctx *c, struct damon_region *r,
134 struct damos *s)
135 {
136 int hotness = damon_hot_score(c, r, s);
137
138 /* Return coldness of the region */
139 return DAMOS_MAX_SCORE - hotness;
140 }
141