3 * The cache is base on a hash of the page address
5 * Copyright 2012 Red Hat, Inc. and/or its affiliates
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 "migration/page_cache.h"
24 #define DPRINTF(fmt, ...) \
25 do { fprintf(stdout, "cache: " fmt, ## __VA_ARGS__); } while (0)
27 #define DPRINTF(fmt, ...) \
31 /* the page in cache will not be replaced in two cycles */
32 #define CACHED_PAGE_LIFETIME 2
34 typedef struct CacheItem CacheItem;
43 CacheItem *page_cache;
49 PageCache *cache_init(int64_t new_size, size_t page_size, Error **errp)
52 size_t num_pages = new_size / page_size;
55 if (new_size < page_size) {
56 error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
57 "is smaller than one target page size");
61 /* We prefer not to abort if there is no memory */
62 cache = g_try_malloc(sizeof(*cache));
64 error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
65 "Failed to allocate cache");
68 /* round down to the nearest power of 2 */
69 if (!is_power_of_2(num_pages)) {
70 num_pages = pow2floor(num_pages);
71 DPRINTF("rounding down to %" PRId64 "\n", num_pages);
73 cache->page_size = page_size;
75 cache->max_num_items = num_pages;
77 DPRINTF("Setting cache buckets to %" PRId64 "\n", cache->max_num_items);
79 /* We prefer not to abort if there is no memory */
80 cache->page_cache = g_try_malloc((cache->max_num_items) *
81 sizeof(*cache->page_cache));
82 if (!cache->page_cache) {
83 error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
84 "Failed to allocate page cache");
89 for (i = 0; i < cache->max_num_items; i++) {
90 cache->page_cache[i].it_data = NULL;
91 cache->page_cache[i].it_age = 0;
92 cache->page_cache[i].it_addr = -1;
98 void cache_fini(PageCache *cache)
103 g_assert(cache->page_cache);
105 for (i = 0; i < cache->max_num_items; i++) {
106 g_free(cache->page_cache[i].it_data);
109 g_free(cache->page_cache);
110 cache->page_cache = NULL;
114 static size_t cache_get_cache_pos(const PageCache *cache,
117 g_assert(cache->max_num_items);
118 return (address / cache->page_size) & (cache->max_num_items - 1);
121 static CacheItem *cache_get_by_addr(const PageCache *cache, uint64_t addr)
126 g_assert(cache->page_cache);
128 pos = cache_get_cache_pos(cache, addr);
130 return &cache->page_cache[pos];
133 uint8_t *get_cached_data(const PageCache *cache, uint64_t addr)
135 return cache_get_by_addr(cache, addr)->it_data;
138 bool cache_is_cached(const PageCache *cache, uint64_t addr,
139 uint64_t current_age)
143 it = cache_get_by_addr(cache, addr);
145 if (it->it_addr == addr) {
146 /* update the it_age when the cache hit */
147 it->it_age = current_age;
153 int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata,
154 uint64_t current_age)
159 /* actual update of entry */
160 it = cache_get_by_addr(cache, addr);
162 if (it->it_data && it->it_addr != addr &&
163 it->it_age + CACHED_PAGE_LIFETIME > current_age) {
164 /* the cache page is fresh, don't replace it */
169 it->it_data = g_try_malloc(cache->page_size);
171 DPRINTF("Error allocating page\n");
177 memcpy(it->it_data, pdata, cache->page_size);
179 it->it_age = current_age;