hw/arm/virt: use VirtMachineState.gic_version
[qemu.git] / page_cache.c
1 /*
2 * Page cache for QEMU
3 * The cache is base on a hash of the page address
4 *
5 * Copyright 2012 Red Hat, Inc. and/or its affiliates
6 *
7 * Authors:
8 * Orit Wasserman <owasserm@redhat.com>
9 *
10 * This work is licensed under the terms of the GNU GPL, version 2 or later.
11 * See the COPYING file in the top-level directory.
12 *
13 */
14
15 #include "qemu/osdep.h"
16
17 #include "qemu-common.h"
18 #include "qemu/host-utils.h"
19 #include "migration/page_cache.h"
20
21 #ifdef DEBUG_CACHE
22 #define DPRINTF(fmt, ...) \
23 do { fprintf(stdout, "cache: " fmt, ## __VA_ARGS__); } while (0)
24 #else
25 #define DPRINTF(fmt, ...) \
26 do { } while (0)
27 #endif
28
29 /* the page in cache will not be replaced in two cycles */
30 #define CACHED_PAGE_LIFETIME 2
31
32 typedef struct CacheItem CacheItem;
33
34 struct CacheItem {
35 uint64_t it_addr;
36 uint64_t it_age;
37 uint8_t *it_data;
38 };
39
40 struct PageCache {
41 CacheItem *page_cache;
42 unsigned int page_size;
43 int64_t max_num_items;
44 uint64_t max_item_age;
45 int64_t num_items;
46 };
47
48 PageCache *cache_init(int64_t num_pages, unsigned int page_size)
49 {
50 int64_t i;
51
52 PageCache *cache;
53
54 if (num_pages <= 0) {
55 DPRINTF("invalid number of pages\n");
56 return NULL;
57 }
58
59 /* We prefer not to abort if there is no memory */
60 cache = g_try_malloc(sizeof(*cache));
61 if (!cache) {
62 DPRINTF("Failed to allocate cache\n");
63 return NULL;
64 }
65 /* round down to the nearest power of 2 */
66 if (!is_power_of_2(num_pages)) {
67 num_pages = pow2floor(num_pages);
68 DPRINTF("rounding down to %" PRId64 "\n", num_pages);
69 }
70 cache->page_size = page_size;
71 cache->num_items = 0;
72 cache->max_item_age = 0;
73 cache->max_num_items = num_pages;
74
75 DPRINTF("Setting cache buckets to %" PRId64 "\n", cache->max_num_items);
76
77 /* We prefer not to abort if there is no memory */
78 cache->page_cache = g_try_malloc((cache->max_num_items) *
79 sizeof(*cache->page_cache));
80 if (!cache->page_cache) {
81 DPRINTF("Failed to allocate cache->page_cache\n");
82 g_free(cache);
83 return NULL;
84 }
85
86 for (i = 0; i < cache->max_num_items; i++) {
87 cache->page_cache[i].it_data = NULL;
88 cache->page_cache[i].it_age = 0;
89 cache->page_cache[i].it_addr = -1;
90 }
91
92 return cache;
93 }
94
95 void cache_fini(PageCache *cache)
96 {
97 int64_t i;
98
99 g_assert(cache);
100 g_assert(cache->page_cache);
101
102 for (i = 0; i < cache->max_num_items; i++) {
103 g_free(cache->page_cache[i].it_data);
104 }
105
106 g_free(cache->page_cache);
107 cache->page_cache = NULL;
108 g_free(cache);
109 }
110
111 static size_t cache_get_cache_pos(const PageCache *cache,
112 uint64_t address)
113 {
114 g_assert(cache->max_num_items);
115 return (address / cache->page_size) & (cache->max_num_items - 1);
116 }
117
118 static CacheItem *cache_get_by_addr(const PageCache *cache, uint64_t addr)
119 {
120 size_t pos;
121
122 g_assert(cache);
123 g_assert(cache->page_cache);
124
125 pos = cache_get_cache_pos(cache, addr);
126
127 return &cache->page_cache[pos];
128 }
129
130 uint8_t *get_cached_data(const PageCache *cache, uint64_t addr)
131 {
132 return cache_get_by_addr(cache, addr)->it_data;
133 }
134
135 bool cache_is_cached(const PageCache *cache, uint64_t addr,
136 uint64_t current_age)
137 {
138 CacheItem *it;
139
140 it = cache_get_by_addr(cache, addr);
141
142 if (it->it_addr == addr) {
143 /* update the it_age when the cache hit */
144 it->it_age = current_age;
145 return true;
146 }
147 return false;
148 }
149
150 int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata,
151 uint64_t current_age)
152 {
153
154 CacheItem *it;
155
156 /* actual update of entry */
157 it = cache_get_by_addr(cache, addr);
158
159 if (it->it_data && it->it_addr != addr &&
160 it->it_age + CACHED_PAGE_LIFETIME > current_age) {
161 /* the cache page is fresh, don't replace it */
162 return -1;
163 }
164 /* allocate page */
165 if (!it->it_data) {
166 it->it_data = g_try_malloc(cache->page_size);
167 if (!it->it_data) {
168 DPRINTF("Error allocating page\n");
169 return -1;
170 }
171 cache->num_items++;
172 }
173
174 memcpy(it->it_data, pdata, cache->page_size);
175
176 it->it_age = current_age;
177 it->it_addr = addr;
178
179 return 0;
180 }
181
182 int64_t cache_resize(PageCache *cache, int64_t new_num_pages)
183 {
184 PageCache *new_cache;
185 int64_t i;
186
187 CacheItem *old_it, *new_it;
188
189 g_assert(cache);
190
191 /* cache was not inited */
192 if (cache->page_cache == NULL) {
193 return -1;
194 }
195
196 /* same size */
197 if (pow2floor(new_num_pages) == cache->max_num_items) {
198 return cache->max_num_items;
199 }
200
201 new_cache = cache_init(new_num_pages, cache->page_size);
202 if (!(new_cache)) {
203 DPRINTF("Error creating new cache\n");
204 return -1;
205 }
206
207 /* move all data from old cache */
208 for (i = 0; i < cache->max_num_items; i++) {
209 old_it = &cache->page_cache[i];
210 if (old_it->it_addr != -1) {
211 /* check for collision, if there is, keep MRU page */
212 new_it = cache_get_by_addr(new_cache, old_it->it_addr);
213 if (new_it->it_data && new_it->it_age >= old_it->it_age) {
214 /* keep the MRU page */
215 g_free(old_it->it_data);
216 } else {
217 if (!new_it->it_data) {
218 new_cache->num_items++;
219 }
220 g_free(new_it->it_data);
221 new_it->it_data = old_it->it_data;
222 new_it->it_age = old_it->it_age;
223 new_it->it_addr = old_it->it_addr;
224 }
225 }
226 }
227
228 g_free(cache->page_cache);
229 cache->page_cache = new_cache->page_cache;
230 cache->max_num_items = new_cache->max_num_items;
231 cache->num_items = new_cache->num_items;
232
233 g_free(new_cache);
234
235 return cache->max_num_items;
236 }