qemu-iotests: Try setting cache mode for children
[qemu.git] / page_cache.c
bloba9eb0769b3077379b231e267bde53ea83cf0159e
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 <stdint.h>
16 #include <stdio.h>
17 #include <stdlib.h>
18 #include <string.h>
19 #include <sys/time.h>
20 #include <sys/types.h>
21 #include <stdbool.h>
22 #include <glib.h>
24 #include "qemu-common.h"
25 #include "migration/page_cache.h"
27 #ifdef DEBUG_CACHE
28 #define DPRINTF(fmt, ...) \
29 do { fprintf(stdout, "cache: " fmt, ## __VA_ARGS__); } while (0)
30 #else
31 #define DPRINTF(fmt, ...) \
32 do { } while (0)
33 #endif
35 /* the page in cache will not be replaced in two cycles */
36 #define CACHED_PAGE_LIFETIME 2
38 typedef struct CacheItem CacheItem;
40 struct CacheItem {
41 uint64_t it_addr;
42 uint64_t it_age;
43 uint8_t *it_data;
46 struct PageCache {
47 CacheItem *page_cache;
48 unsigned int page_size;
49 int64_t max_num_items;
50 uint64_t max_item_age;
51 int64_t num_items;
54 PageCache *cache_init(int64_t num_pages, unsigned int page_size)
56 int64_t i;
58 PageCache *cache;
60 if (num_pages <= 0) {
61 DPRINTF("invalid number of pages\n");
62 return NULL;
65 /* We prefer not to abort if there is no memory */
66 cache = g_try_malloc(sizeof(*cache));
67 if (!cache) {
68 DPRINTF("Failed to allocate cache\n");
69 return NULL;
71 /* round down to the nearest power of 2 */
72 if (!is_power_of_2(num_pages)) {
73 num_pages = pow2floor(num_pages);
74 DPRINTF("rounding down to %" PRId64 "\n", num_pages);
76 cache->page_size = page_size;
77 cache->num_items = 0;
78 cache->max_item_age = 0;
79 cache->max_num_items = num_pages;
81 DPRINTF("Setting cache buckets to %" PRId64 "\n", cache->max_num_items);
83 /* We prefer not to abort if there is no memory */
84 cache->page_cache = g_try_malloc((cache->max_num_items) *
85 sizeof(*cache->page_cache));
86 if (!cache->page_cache) {
87 DPRINTF("Failed to allocate cache->page_cache\n");
88 g_free(cache);
89 return NULL;
92 for (i = 0; i < cache->max_num_items; i++) {
93 cache->page_cache[i].it_data = NULL;
94 cache->page_cache[i].it_age = 0;
95 cache->page_cache[i].it_addr = -1;
98 return cache;
101 void cache_fini(PageCache *cache)
103 int64_t i;
105 g_assert(cache);
106 g_assert(cache->page_cache);
108 for (i = 0; i < cache->max_num_items; i++) {
109 g_free(cache->page_cache[i].it_data);
112 g_free(cache->page_cache);
113 cache->page_cache = NULL;
114 g_free(cache);
117 static size_t cache_get_cache_pos(const PageCache *cache,
118 uint64_t address)
120 size_t pos;
122 g_assert(cache->max_num_items);
123 pos = (address / cache->page_size) & (cache->max_num_items - 1);
124 return pos;
127 static CacheItem *cache_get_by_addr(const PageCache *cache, uint64_t addr)
129 size_t pos;
131 g_assert(cache);
132 g_assert(cache->page_cache);
134 pos = cache_get_cache_pos(cache, addr);
136 return &cache->page_cache[pos];
139 uint8_t *get_cached_data(const PageCache *cache, uint64_t addr)
141 return cache_get_by_addr(cache, addr)->it_data;
144 bool cache_is_cached(const PageCache *cache, uint64_t addr,
145 uint64_t current_age)
147 CacheItem *it;
149 it = cache_get_by_addr(cache, addr);
151 if (it->it_addr == addr) {
152 /* update the it_age when the cache hit */
153 it->it_age = current_age;
154 return true;
156 return false;
159 int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata,
160 uint64_t current_age)
163 CacheItem *it;
165 /* actual update of entry */
166 it = cache_get_by_addr(cache, addr);
168 if (it->it_data && it->it_addr != addr &&
169 it->it_age + CACHED_PAGE_LIFETIME > current_age) {
170 /* the cache page is fresh, don't replace it */
171 return -1;
173 /* allocate page */
174 if (!it->it_data) {
175 it->it_data = g_try_malloc(cache->page_size);
176 if (!it->it_data) {
177 DPRINTF("Error allocating page\n");
178 return -1;
180 cache->num_items++;
183 memcpy(it->it_data, pdata, cache->page_size);
185 it->it_age = current_age;
186 it->it_addr = addr;
188 return 0;
191 int64_t cache_resize(PageCache *cache, int64_t new_num_pages)
193 PageCache *new_cache;
194 int64_t i;
196 CacheItem *old_it, *new_it;
198 g_assert(cache);
200 /* cache was not inited */
201 if (cache->page_cache == NULL) {
202 return -1;
205 /* same size */
206 if (pow2floor(new_num_pages) == cache->max_num_items) {
207 return cache->max_num_items;
210 new_cache = cache_init(new_num_pages, cache->page_size);
211 if (!(new_cache)) {
212 DPRINTF("Error creating new cache\n");
213 return -1;
216 /* move all data from old cache */
217 for (i = 0; i < cache->max_num_items; i++) {
218 old_it = &cache->page_cache[i];
219 if (old_it->it_addr != -1) {
220 /* check for collision, if there is, keep MRU page */
221 new_it = cache_get_by_addr(new_cache, old_it->it_addr);
222 if (new_it->it_data && new_it->it_age >= old_it->it_age) {
223 /* keep the MRU page */
224 g_free(old_it->it_data);
225 } else {
226 if (!new_it->it_data) {
227 new_cache->num_items++;
229 g_free(new_it->it_data);
230 new_it->it_data = old_it->it_data;
231 new_it->it_age = old_it->it_age;
232 new_it->it_addr = old_it->it_addr;
237 g_free(cache->page_cache);
238 cache->page_cache = new_cache->page_cache;
239 cache->max_num_items = new_cache->max_num_items;
240 cache->num_items = new_cache->num_items;
242 g_free(new_cache);
244 return cache->max_num_items;