1
2
3
4#include <linux/mm.h>
5#include <linux/init.h>
6#include <linux/mmzone.h>
7#include <linux/random.h>
8#include <linux/moduleparam.h>
9#include "internal.h"
10#include "shuffle.h"
11
12DEFINE_STATIC_KEY_FALSE(page_alloc_shuffle_key);
13
14static bool shuffle_param;
15static int shuffle_show(char *buffer, const struct kernel_param *kp)
16{
17 return sprintf(buffer, "%c\n", shuffle_param ? 'Y' : 'N');
18}
19
20static __meminit int shuffle_store(const char *val,
21 const struct kernel_param *kp)
22{
23 int rc = param_set_bool(val, kp);
24
25 if (rc < 0)
26 return rc;
27 if (shuffle_param)
28 static_branch_enable(&page_alloc_shuffle_key);
29 return 0;
30}
31module_param_call(shuffle, shuffle_store, shuffle_show, &shuffle_param, 0400);
32
33
34
35
36
37static struct page * __meminit shuffle_valid_page(struct zone *zone,
38 unsigned long pfn, int order)
39{
40 struct page *page = pfn_to_online_page(pfn);
41
42
43
44
45
46
47
48 if (!page)
49 return NULL;
50
51
52 if (page_zone(page) != zone)
53 return NULL;
54
55
56 if (!PageBuddy(page))
57 return NULL;
58
59
60
61
62
63 if (buddy_order(page) != order)
64 return NULL;
65
66 return page;
67}
68
69
70
71
72
73
74
75
76
77
78
79
80#define SHUFFLE_RETRY 10
81void __meminit __shuffle_zone(struct zone *z)
82{
83 unsigned long i, flags;
84 unsigned long start_pfn = z->zone_start_pfn;
85 unsigned long end_pfn = zone_end_pfn(z);
86 const int order = SHUFFLE_ORDER;
87 const int order_pages = 1 << order;
88
89 spin_lock_irqsave(&z->lock, flags);
90 start_pfn = ALIGN(start_pfn, order_pages);
91 for (i = start_pfn; i < end_pfn; i += order_pages) {
92 unsigned long j;
93 int migratetype, retry;
94 struct page *page_i, *page_j;
95
96
97
98
99
100
101
102 page_i = shuffle_valid_page(z, i, order);
103 if (!page_i)
104 continue;
105
106 for (retry = 0; retry < SHUFFLE_RETRY; retry++) {
107
108
109
110
111
112
113 j = z->zone_start_pfn +
114 ALIGN_DOWN(get_random_long() % z->spanned_pages,
115 order_pages);
116 page_j = shuffle_valid_page(z, j, order);
117 if (page_j && page_j != page_i)
118 break;
119 }
120 if (retry >= SHUFFLE_RETRY) {
121 pr_debug("%s: failed to swap %#lx\n", __func__, i);
122 continue;
123 }
124
125
126
127
128
129
130 migratetype = get_pageblock_migratetype(page_i);
131 if (get_pageblock_migratetype(page_j) != migratetype) {
132 pr_debug("%s: migratetype mismatch %#lx\n", __func__, i);
133 continue;
134 }
135
136 list_swap(&page_i->lru, &page_j->lru);
137
138 pr_debug("%s: swap: %#lx -> %#lx\n", __func__, i, j);
139
140
141 if ((i % (100 * order_pages)) == 0) {
142 spin_unlock_irqrestore(&z->lock, flags);
143 cond_resched();
144 spin_lock_irqsave(&z->lock, flags);
145 }
146 }
147 spin_unlock_irqrestore(&z->lock, flags);
148}
149
150
151
152
153
154void __meminit __shuffle_free_memory(pg_data_t *pgdat)
155{
156 struct zone *z;
157
158 for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
159 shuffle_zone(z);
160}
161
162bool shuffle_pick_tail(void)
163{
164 static u64 rand;
165 static u8 rand_bits;
166 bool ret;
167
168
169
170
171
172 if (rand_bits == 0) {
173 rand_bits = 64;
174 rand = get_random_u64();
175 }
176
177 ret = rand & 1;
178
179 rand_bits--;
180 rand >>= 1;
181
182 return ret;
183}
184