block: Add BlockDriver.bdrv_gather_child_options
[qemu/ar7.git] / migration / page_cache.c
blobacc252b100292935569a937a93ef126d5c4c0d01
1 /*
2 * Page cache for QEMU
3 * The cache is base on a hash of the page address
5 * Copyright 2012 Red Hat, Inc. and/or its affiliates
7 * Authors:
8 * Orit Wasserman <owasserm@redhat.com>
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.
15 #include "qemu/osdep.h"
17 #include "qapi/qmp/qerror.h"
18 #include "qapi/error.h"
19 #include "qemu-common.h"
20 #include "qemu/host-utils.h"
21 #include "page_cache.h"
23 #ifdef DEBUG_CACHE
24 #define DPRINTF(fmt, ...) \
25 do { fprintf(stdout, "cache: " fmt, ## __VA_ARGS__); } while (0)
26 #else
27 #define DPRINTF(fmt, ...) \
28 do { } while (0)
29 #endif
31 /* the page in cache will not be replaced in two cycles */
32 #define CACHED_PAGE_LIFETIME 2
34 typedef struct CacheItem CacheItem;
36 struct CacheItem {
37 uint64_t it_addr;
38 uint64_t it_age;
39 uint8_t *it_data;
42 struct PageCache {
43 CacheItem *page_cache;
44 size_t page_size;
45 size_t max_num_items;
46 size_t num_items;
49 PageCache *cache_init(int64_t new_size, size_t page_size, Error **errp)
51 int64_t i;
52 size_t num_pages = new_size / page_size;
53 PageCache *cache;
55 if (new_size < page_size) {
56 error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
57 "is smaller than one target page size");
58 return NULL;
61 /* round down to the nearest power of 2 */
62 if (!is_power_of_2(num_pages)) {
63 error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
64 "is not a power of two number of pages");
65 return NULL;
68 /* We prefer not to abort if there is no memory */
69 cache = g_try_malloc(sizeof(*cache));
70 if (!cache) {
71 error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
72 "Failed to allocate cache");
73 return NULL;
75 cache->page_size = page_size;
76 cache->num_items = 0;
77 cache->max_num_items = num_pages;
79 DPRINTF("Setting cache buckets to %" PRId64 "\n", cache->max_num_items);
81 /* We prefer not to abort if there is no memory */
82 cache->page_cache = g_try_malloc((cache->max_num_items) *
83 sizeof(*cache->page_cache));
84 if (!cache->page_cache) {
85 error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
86 "Failed to allocate page cache");
87 g_free(cache);
88 return NULL;
91 for (i = 0; i < cache->max_num_items; i++) {
92 cache->page_cache[i].it_data = NULL;
93 cache->page_cache[i].it_age = 0;
94 cache->page_cache[i].it_addr = -1;
97 return cache;
100 void cache_fini(PageCache *cache)
102 int64_t i;
104 g_assert(cache);
105 g_assert(cache->page_cache);
107 for (i = 0; i < cache->max_num_items; i++) {
108 g_free(cache->page_cache[i].it_data);
111 g_free(cache->page_cache);
112 cache->page_cache = NULL;
113 g_free(cache);
116 static size_t cache_get_cache_pos(const PageCache *cache,
117 uint64_t address)
119 g_assert(cache->max_num_items);
120 return (address / cache->page_size) & (cache->max_num_items - 1);
123 static CacheItem *cache_get_by_addr(const PageCache *cache, uint64_t addr)
125 size_t pos;
127 g_assert(cache);
128 g_assert(cache->page_cache);
130 pos = cache_get_cache_pos(cache, addr);
132 return &cache->page_cache[pos];
135 uint8_t *get_cached_data(const PageCache *cache, uint64_t addr)
137 return cache_get_by_addr(cache, addr)->it_data;
140 bool cache_is_cached(const PageCache *cache, uint64_t addr,
141 uint64_t current_age)
143 CacheItem *it;
145 it = cache_get_by_addr(cache, addr);
147 if (it->it_addr == addr) {
148 /* update the it_age when the cache hit */
149 it->it_age = current_age;
150 return true;
152 return false;
155 int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata,
156 uint64_t current_age)
159 CacheItem *it;
161 /* actual update of entry */
162 it = cache_get_by_addr(cache, addr);
164 if (it->it_data && it->it_addr != addr &&
165 it->it_age + CACHED_PAGE_LIFETIME > current_age) {
166 /* the cache page is fresh, don't replace it */
167 return -1;
169 /* allocate page */
170 if (!it->it_data) {
171 it->it_data = g_try_malloc(cache->page_size);
172 if (!it->it_data) {
173 DPRINTF("Error allocating page\n");
174 return -1;
176 cache->num_items++;
179 memcpy(it->it_data, pdata, cache->page_size);
181 it->it_age = current_age;
182 it->it_addr = addr;
184 return 0;