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Orit Wasserman9fb26642012-08-06 21:42:50 +03001/*
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
Peter Maydelld38ea872016-01-29 17:50:05 +000015#include "qemu/osdep.h"
Orit Wasserman9fb26642012-08-06 21:42:50 +030016
Juan Quintela80f8dfd2017-10-06 22:30:45 +020017#include "qapi/qmp/qerror.h"
18#include "qapi/error.h"
Paolo Bonzini87776ab2016-03-15 15:36:13 +010019#include "qemu/host-utils.h"
Michael S. Tsirkin53d37d32018-05-03 22:50:51 +030020#include "page_cache.h"
Bihong Yufe80c022020-10-20 15:32:56 +080021#include "trace.h"
Orit Wasserman9fb26642012-08-06 21:42:50 +030022
ChenLiang27af7d62014-11-24 19:55:47 +080023/* the page in cache will not be replaced in two cycles */
24#define CACHED_PAGE_LIFETIME 2
25
Orit Wasserman9fb26642012-08-06 21:42:50 +030026typedef struct CacheItem CacheItem;
27
28struct CacheItem {
29 uint64_t it_addr;
30 uint64_t it_age;
31 uint8_t *it_data;
32};
33
34struct PageCache {
35 CacheItem *page_cache;
Juan Quintela9ca3f962017-10-06 18:17:41 +020036 size_t page_size;
37 size_t max_num_items;
38 size_t num_items;
Orit Wasserman9fb26642012-08-06 21:42:50 +030039};
40
Markus Armbruster8b9407a2021-02-02 15:17:32 +010041PageCache *cache_init(uint64_t new_size, size_t page_size, Error **errp)
Orit Wasserman9fb26642012-08-06 21:42:50 +030042{
43 int64_t i;
Juan Quintela80f8dfd2017-10-06 22:30:45 +020044 size_t num_pages = new_size / page_size;
Orit Wasserman9fb26642012-08-06 21:42:50 +030045 PageCache *cache;
46
Juan Quintela80f8dfd2017-10-06 22:30:45 +020047 if (new_size < page_size) {
48 error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
49 "is smaller than one target page size");
Orit Wasserman9fb26642012-08-06 21:42:50 +030050 return NULL;
51 }
52
Juan Quintelabab01ed2017-10-06 22:58:44 +020053 /* round down to the nearest power of 2 */
54 if (!is_power_of_2(num_pages)) {
55 error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
56 "is not a power of two number of pages");
57 return NULL;
58 }
59
Orit Wassermana17b2fd2014-01-30 20:08:37 +020060 /* We prefer not to abort if there is no memory */
61 cache = g_try_malloc(sizeof(*cache));
62 if (!cache) {
Markus Armbruster7bfc4792021-02-02 15:17:33 +010063 error_setg(errp, "Failed to allocate cache");
Orit Wassermana17b2fd2014-01-30 20:08:37 +020064 return NULL;
65 }
Orit Wasserman9fb26642012-08-06 21:42:50 +030066 cache->page_size = page_size;
67 cache->num_items = 0;
Orit Wasserman9fb26642012-08-06 21:42:50 +030068 cache->max_num_items = num_pages;
69
Bihong Yufe80c022020-10-20 15:32:56 +080070 trace_migration_pagecache_init(cache->max_num_items);
Orit Wasserman9fb26642012-08-06 21:42:50 +030071
Orit Wassermana17b2fd2014-01-30 20:08:37 +020072 /* We prefer not to abort if there is no memory */
73 cache->page_cache = g_try_malloc((cache->max_num_items) *
74 sizeof(*cache->page_cache));
75 if (!cache->page_cache) {
Markus Armbruster7bfc4792021-02-02 15:17:33 +010076 error_setg(errp, "Failed to allocate page cache");
Orit Wassermana17b2fd2014-01-30 20:08:37 +020077 g_free(cache);
78 return NULL;
79 }
Orit Wasserman9fb26642012-08-06 21:42:50 +030080
81 for (i = 0; i < cache->max_num_items; i++) {
82 cache->page_cache[i].it_data = NULL;
83 cache->page_cache[i].it_age = 0;
84 cache->page_cache[i].it_addr = -1;
85 }
86
87 return cache;
88}
89
90void cache_fini(PageCache *cache)
91{
92 int64_t i;
93
94 g_assert(cache);
95 g_assert(cache->page_cache);
96
97 for (i = 0; i < cache->max_num_items; i++) {
98 g_free(cache->page_cache[i].it_data);
99 }
100
101 g_free(cache->page_cache);
102 cache->page_cache = NULL;
Chen Gang4380be02014-06-02 20:16:55 +0800103 g_free(cache);
Orit Wasserman9fb26642012-08-06 21:42:50 +0300104}
105
106static size_t cache_get_cache_pos(const PageCache *cache,
107 uint64_t address)
108{
Orit Wasserman9fb26642012-08-06 21:42:50 +0300109 g_assert(cache->max_num_items);
Eduardo Habkost9be38592016-06-13 18:57:58 -0300110 return (address / cache->page_size) & (cache->max_num_items - 1);
Orit Wasserman9fb26642012-08-06 21:42:50 +0300111}
112
Orit Wasserman9fb26642012-08-06 21:42:50 +0300113static CacheItem *cache_get_by_addr(const PageCache *cache, uint64_t addr)
114{
115 size_t pos;
116
117 g_assert(cache);
118 g_assert(cache->page_cache);
119
120 pos = cache_get_cache_pos(cache, addr);
121
122 return &cache->page_cache[pos];
123}
124
125uint8_t *get_cached_data(const PageCache *cache, uint64_t addr)
126{
127 return cache_get_by_addr(cache, addr)->it_data;
128}
129
ChenLiang1b826f22014-11-24 19:55:48 +0800130bool cache_is_cached(const PageCache *cache, uint64_t addr,
131 uint64_t current_age)
132{
133 CacheItem *it;
134
135 it = cache_get_by_addr(cache, addr);
136
137 if (it->it_addr == addr) {
138 /* update the it_age when the cache hit */
139 it->it_age = current_age;
140 return true;
141 }
142 return false;
143}
144
ChenLiang27af7d62014-11-24 19:55:47 +0800145int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata,
146 uint64_t current_age)
Orit Wasserman9fb26642012-08-06 21:42:50 +0300147{
148
ChenLiang1b826f22014-11-24 19:55:48 +0800149 CacheItem *it;
Orit Wasserman9fb26642012-08-06 21:42:50 +0300150
151 /* actual update of entry */
152 it = cache_get_by_addr(cache, addr);
153
ChenLiang27af7d62014-11-24 19:55:47 +0800154 if (it->it_data && it->it_addr != addr &&
155 it->it_age + CACHED_PAGE_LIFETIME > current_age) {
156 /* the cache page is fresh, don't replace it */
157 return -1;
158 }
Orit Wasserman89db9982014-01-30 20:08:38 +0200159 /* allocate page */
Orit Wasserman9fb26642012-08-06 21:42:50 +0300160 if (!it->it_data) {
Orit Wasserman89db9982014-01-30 20:08:38 +0200161 it->it_data = g_try_malloc(cache->page_size);
162 if (!it->it_data) {
Bihong Yufe80c022020-10-20 15:32:56 +0800163 trace_migration_pagecache_insert();
Orit Wasserman89db9982014-01-30 20:08:38 +0200164 return -1;
165 }
Orit Wasserman9fb26642012-08-06 21:42:50 +0300166 cache->num_items++;
167 }
168
Orit Wasserman89db9982014-01-30 20:08:38 +0200169 memcpy(it->it_data, pdata, cache->page_size);
170
ChenLiang27af7d62014-11-24 19:55:47 +0800171 it->it_age = current_age;
Orit Wasserman9fb26642012-08-06 21:42:50 +0300172 it->it_addr = addr;
Orit Wasserman89db9982014-01-30 20:08:38 +0200173
174 return 0;
Orit Wasserman9fb26642012-08-06 21:42:50 +0300175}