--- /dev/null
+/*
+ * Page cache for QEMU
+ * The cache is base on a hash of the page address
+ *
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Orit Wasserman <owasserm@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <strings.h>
+#include <string.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <stdbool.h>
+#include <glib.h>
+
+#include "qemu-common.h"
+#include "migration/page_cache.h"
+
+#ifdef DEBUG_CACHE
+#define DPRINTF(fmt, ...) \
+ do { fprintf(stdout, "cache: " fmt, ## __VA_ARGS__); } while (0)
+#else
+#define DPRINTF(fmt, ...) \
+ do { } while (0)
+#endif
+
+/* the page in cache will not be replaced in two cycles */
+#define CACHED_PAGE_LIFETIME 2
+
+typedef struct CacheItem CacheItem;
+
+struct CacheItem {
+ uint64_t it_addr;
+ uint64_t it_age;
+ uint8_t *it_data;
+};
+
+struct PageCache {
+ CacheItem *page_cache;
+ unsigned int page_size;
+ int64_t max_num_items;
+ uint64_t max_item_age;
+ int64_t num_items;
+};
+
+PageCache *cache_init(int64_t num_pages, unsigned int page_size)
+{
+ int64_t i;
+
+ PageCache *cache;
+
+ if (num_pages <= 0) {
+ DPRINTF("invalid number of pages\n");
+ return NULL;
+ }
+
+ /* We prefer not to abort if there is no memory */
+ cache = g_try_malloc(sizeof(*cache));
+ if (!cache) {
+ DPRINTF("Failed to allocate cache\n");
+ return NULL;
+ }
+ /* round down to the nearest power of 2 */
+ if (!is_power_of_2(num_pages)) {
+ num_pages = pow2floor(num_pages);
+ DPRINTF("rounding down to %" PRId64 "\n", num_pages);
+ }
+ cache->page_size = page_size;
+ cache->num_items = 0;
+ cache->max_item_age = 0;
+ cache->max_num_items = num_pages;
+
+ DPRINTF("Setting cache buckets to %" PRId64 "\n", cache->max_num_items);
+
+ /* We prefer not to abort if there is no memory */
+ cache->page_cache = g_try_malloc((cache->max_num_items) *
+ sizeof(*cache->page_cache));
+ if (!cache->page_cache) {
+ DPRINTF("Failed to allocate cache->page_cache\n");
+ g_free(cache);
+ return NULL;
+ }
+
+ for (i = 0; i < cache->max_num_items; i++) {
+ cache->page_cache[i].it_data = NULL;
+ cache->page_cache[i].it_age = 0;
+ cache->page_cache[i].it_addr = -1;
+ }
+
+ return cache;
+}
+
+void cache_fini(PageCache *cache)
+{
+ int64_t i;
+
+ g_assert(cache);
+ g_assert(cache->page_cache);
+
+ for (i = 0; i < cache->max_num_items; i++) {
+ g_free(cache->page_cache[i].it_data);
+ }
+
+ g_free(cache->page_cache);
+ cache->page_cache = NULL;
+ g_free(cache);
+}
+
+static size_t cache_get_cache_pos(const PageCache *cache,
+ uint64_t address)
+{
+ size_t pos;
+
+ g_assert(cache->max_num_items);
+ pos = (address / cache->page_size) & (cache->max_num_items - 1);
+ return pos;
+}
+
+static CacheItem *cache_get_by_addr(const PageCache *cache, uint64_t addr)
+{
+ size_t pos;
+
+ g_assert(cache);
+ g_assert(cache->page_cache);
+
+ pos = cache_get_cache_pos(cache, addr);
+
+ return &cache->page_cache[pos];
+}
+
+uint8_t *get_cached_data(const PageCache *cache, uint64_t addr)
+{
+ return cache_get_by_addr(cache, addr)->it_data;
+}
+
+bool cache_is_cached(const PageCache *cache, uint64_t addr,
+ uint64_t current_age)
+{
+ CacheItem *it;
+
+ it = cache_get_by_addr(cache, addr);
+
+ if (it->it_addr == addr) {
+ /* update the it_age when the cache hit */
+ it->it_age = current_age;
+ return true;
+ }
+ return false;
+}
+
+int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata,
+ uint64_t current_age)
+{
+
+ CacheItem *it;
+
+ /* actual update of entry */
+ it = cache_get_by_addr(cache, addr);
+
+ if (it->it_data && it->it_addr != addr &&
+ it->it_age + CACHED_PAGE_LIFETIME > current_age) {
+ /* the cache page is fresh, don't replace it */
+ return -1;
+ }
+ /* allocate page */
+ if (!it->it_data) {
+ it->it_data = g_try_malloc(cache->page_size);
+ if (!it->it_data) {
+ DPRINTF("Error allocating page\n");
+ return -1;
+ }
+ cache->num_items++;
+ }
+
+ memcpy(it->it_data, pdata, cache->page_size);
+
+ it->it_age = current_age;
+ it->it_addr = addr;
+
+ return 0;
+}
+
+int64_t cache_resize(PageCache *cache, int64_t new_num_pages)
+{
+ PageCache *new_cache;
+ int64_t i;
+
+ CacheItem *old_it, *new_it;
+
+ g_assert(cache);
+
+ /* cache was not inited */
+ if (cache->page_cache == NULL) {
+ return -1;
+ }
+
+ /* same size */
+ if (pow2floor(new_num_pages) == cache->max_num_items) {
+ return cache->max_num_items;
+ }
+
+ new_cache = cache_init(new_num_pages, cache->page_size);
+ if (!(new_cache)) {
+ DPRINTF("Error creating new cache\n");
+ return -1;
+ }
+
+ /* move all data from old cache */
+ for (i = 0; i < cache->max_num_items; i++) {
+ old_it = &cache->page_cache[i];
+ if (old_it->it_addr != -1) {
+ /* check for collision, if there is, keep MRU page */
+ new_it = cache_get_by_addr(new_cache, old_it->it_addr);
+ if (new_it->it_data && new_it->it_age >= old_it->it_age) {
+ /* keep the MRU page */
+ g_free(old_it->it_data);
+ } else {
+ if (!new_it->it_data) {
+ new_cache->num_items++;
+ }
+ g_free(new_it->it_data);
+ new_it->it_data = old_it->it_data;
+ new_it->it_age = old_it->it_age;
+ new_it->it_addr = old_it->it_addr;
+ }
+ }
+ }
+
+ g_free(cache->page_cache);
+ cache->page_cache = new_cache->page_cache;
+ cache->max_num_items = new_cache->max_num_items;
+ cache->num_items = new_cache->num_items;
+
+ g_free(new_cache);
+
+ return cache->max_num_items;
+}
Code Review / kvmfornfv.git / blobdiff