Orit Wasserman | 9fb2664 | 2012-08-06 21:42:50 +0300 | [diff] [blame] | 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 <stdint.h> |
| 16 | #include <stdio.h> |
| 17 | #include <stdlib.h> |
| 18 | #include <strings.h> |
| 19 | #include <string.h> |
| 20 | #include <sys/time.h> |
| 21 | #include <sys/types.h> |
| 22 | #include <stdbool.h> |
| 23 | #include <glib.h> |
Orit Wasserman | 9fb2664 | 2012-08-06 21:42:50 +0300 | [diff] [blame] | 24 | |
| 25 | #include "qemu-common.h" |
Paolo Bonzini | caf71f8 | 2012-12-17 18:19:50 +0100 | [diff] [blame] | 26 | #include "migration/page_cache.h" |
Orit Wasserman | 9fb2664 | 2012-08-06 21:42:50 +0300 | [diff] [blame] | 27 | |
| 28 | #ifdef DEBUG_CACHE |
| 29 | #define DPRINTF(fmt, ...) \ |
| 30 | do { fprintf(stdout, "cache: " fmt, ## __VA_ARGS__); } while (0) |
| 31 | #else |
| 32 | #define DPRINTF(fmt, ...) \ |
| 33 | do { } while (0) |
| 34 | #endif |
| 35 | |
| 36 | typedef struct CacheItem CacheItem; |
| 37 | |
| 38 | struct CacheItem { |
| 39 | uint64_t it_addr; |
| 40 | uint64_t it_age; |
| 41 | uint8_t *it_data; |
| 42 | }; |
| 43 | |
| 44 | struct PageCache { |
| 45 | CacheItem *page_cache; |
| 46 | unsigned int page_size; |
| 47 | int64_t max_num_items; |
| 48 | uint64_t max_item_age; |
| 49 | int64_t num_items; |
| 50 | }; |
| 51 | |
| 52 | PageCache *cache_init(int64_t num_pages, unsigned int page_size) |
| 53 | { |
| 54 | int64_t i; |
| 55 | |
| 56 | PageCache *cache; |
| 57 | |
| 58 | if (num_pages <= 0) { |
| 59 | DPRINTF("invalid number of pages\n"); |
| 60 | return NULL; |
| 61 | } |
| 62 | |
| 63 | cache = g_malloc(sizeof(*cache)); |
| 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 | cache->page_cache = g_malloc((cache->max_num_items) * |
| 78 | sizeof(*cache->page_cache)); |
| 79 | |
| 80 | for (i = 0; i < cache->max_num_items; i++) { |
| 81 | cache->page_cache[i].it_data = NULL; |
| 82 | cache->page_cache[i].it_age = 0; |
| 83 | cache->page_cache[i].it_addr = -1; |
| 84 | } |
| 85 | |
| 86 | return cache; |
| 87 | } |
| 88 | |
| 89 | void cache_fini(PageCache *cache) |
| 90 | { |
| 91 | int64_t i; |
| 92 | |
| 93 | g_assert(cache); |
| 94 | g_assert(cache->page_cache); |
| 95 | |
| 96 | for (i = 0; i < cache->max_num_items; i++) { |
| 97 | g_free(cache->page_cache[i].it_data); |
| 98 | } |
| 99 | |
| 100 | g_free(cache->page_cache); |
| 101 | cache->page_cache = NULL; |
| 102 | } |
| 103 | |
| 104 | static size_t cache_get_cache_pos(const PageCache *cache, |
| 105 | uint64_t address) |
| 106 | { |
| 107 | size_t pos; |
| 108 | |
| 109 | g_assert(cache->max_num_items); |
| 110 | pos = (address / cache->page_size) & (cache->max_num_items - 1); |
| 111 | return pos; |
| 112 | } |
| 113 | |
| 114 | bool cache_is_cached(const PageCache *cache, uint64_t addr) |
| 115 | { |
| 116 | size_t pos; |
| 117 | |
| 118 | g_assert(cache); |
| 119 | g_assert(cache->page_cache); |
| 120 | |
| 121 | pos = cache_get_cache_pos(cache, addr); |
| 122 | |
| 123 | return (cache->page_cache[pos].it_addr == addr); |
| 124 | } |
| 125 | |
| 126 | static CacheItem *cache_get_by_addr(const PageCache *cache, uint64_t addr) |
| 127 | { |
| 128 | size_t pos; |
| 129 | |
| 130 | g_assert(cache); |
| 131 | g_assert(cache->page_cache); |
| 132 | |
| 133 | pos = cache_get_cache_pos(cache, addr); |
| 134 | |
| 135 | return &cache->page_cache[pos]; |
| 136 | } |
| 137 | |
| 138 | uint8_t *get_cached_data(const PageCache *cache, uint64_t addr) |
| 139 | { |
| 140 | return cache_get_by_addr(cache, addr)->it_data; |
| 141 | } |
| 142 | |
| 143 | void cache_insert(PageCache *cache, uint64_t addr, uint8_t *pdata) |
| 144 | { |
| 145 | |
| 146 | CacheItem *it = NULL; |
| 147 | |
| 148 | g_assert(cache); |
| 149 | g_assert(cache->page_cache); |
| 150 | |
| 151 | /* actual update of entry */ |
| 152 | it = cache_get_by_addr(cache, addr); |
| 153 | |
Peter Lieven | 32a1c08 | 2013-02-25 19:12:03 +0200 | [diff] [blame] | 154 | /* free old cached data if any */ |
| 155 | g_free(it->it_data); |
| 156 | |
Orit Wasserman | 9fb2664 | 2012-08-06 21:42:50 +0300 | [diff] [blame] | 157 | if (!it->it_data) { |
| 158 | cache->num_items++; |
| 159 | } |
| 160 | |
Peter Lieven | ee0b44a | 2013-02-25 19:12:04 +0200 | [diff] [blame] | 161 | it->it_data = g_memdup(pdata, cache->page_size); |
Orit Wasserman | 9fb2664 | 2012-08-06 21:42:50 +0300 | [diff] [blame] | 162 | it->it_age = ++cache->max_item_age; |
| 163 | it->it_addr = addr; |
| 164 | } |
| 165 | |
| 166 | int64_t cache_resize(PageCache *cache, int64_t new_num_pages) |
| 167 | { |
| 168 | PageCache *new_cache; |
| 169 | int64_t i; |
| 170 | |
| 171 | CacheItem *old_it, *new_it; |
| 172 | |
| 173 | g_assert(cache); |
| 174 | |
| 175 | /* cache was not inited */ |
| 176 | if (cache->page_cache == NULL) { |
| 177 | return -1; |
| 178 | } |
| 179 | |
| 180 | /* same size */ |
| 181 | if (pow2floor(new_num_pages) == cache->max_num_items) { |
| 182 | return cache->max_num_items; |
| 183 | } |
| 184 | |
| 185 | new_cache = cache_init(new_num_pages, cache->page_size); |
| 186 | if (!(new_cache)) { |
| 187 | DPRINTF("Error creating new cache\n"); |
| 188 | return -1; |
| 189 | } |
| 190 | |
| 191 | /* move all data from old cache */ |
| 192 | for (i = 0; i < cache->max_num_items; i++) { |
| 193 | old_it = &cache->page_cache[i]; |
| 194 | if (old_it->it_addr != -1) { |
| 195 | /* check for collision, if there is, keep MRU page */ |
| 196 | new_it = cache_get_by_addr(new_cache, old_it->it_addr); |
Orit Wasserman | a0ee203 | 2013-02-25 19:12:02 +0200 | [diff] [blame] | 197 | if (new_it->it_data && new_it->it_age >= old_it->it_age) { |
Orit Wasserman | 9fb2664 | 2012-08-06 21:42:50 +0300 | [diff] [blame] | 198 | /* keep the MRU page */ |
Orit Wasserman | a0ee203 | 2013-02-25 19:12:02 +0200 | [diff] [blame] | 199 | g_free(old_it->it_data); |
Orit Wasserman | 9fb2664 | 2012-08-06 21:42:50 +0300 | [diff] [blame] | 200 | } else { |
Orit Wasserman | a0ee203 | 2013-02-25 19:12:02 +0200 | [diff] [blame] | 201 | if (!new_it->it_data) { |
| 202 | new_cache->num_items++; |
| 203 | } |
| 204 | g_free(new_it->it_data); |
| 205 | new_it->it_data = old_it->it_data; |
| 206 | new_it->it_age = old_it->it_age; |
| 207 | new_it->it_addr = old_it->it_addr; |
Orit Wasserman | 9fb2664 | 2012-08-06 21:42:50 +0300 | [diff] [blame] | 208 | } |
| 209 | } |
| 210 | } |
| 211 | |
Orit Wasserman | 0db65d6 | 2013-02-25 19:12:01 +0200 | [diff] [blame] | 212 | g_free(cache->page_cache); |
Orit Wasserman | 9fb2664 | 2012-08-06 21:42:50 +0300 | [diff] [blame] | 213 | cache->page_cache = new_cache->page_cache; |
| 214 | cache->max_num_items = new_cache->max_num_items; |
| 215 | cache->num_items = new_cache->num_items; |
| 216 | |
| 217 | g_free(new_cache); |
| 218 | |
| 219 | return cache->max_num_items; |
| 220 | } |