diff options
Diffstat (limited to 'page_cache.c')
| -rw-r--r-- | page_cache.c | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/page_cache.c b/page_cache.c new file mode 100644 index 0000000000..0294f7e9f6 --- /dev/null +++ b/page_cache.c @@ -0,0 +1,218 @@ +/* + * 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 <strings.h> + +#include "qemu-common.h" +#include "qemu/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 + +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; + } + + cache = g_malloc(sizeof(*cache)); + + /* 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); + + cache->page_cache = g_malloc((cache->max_num_items) * + sizeof(*cache->page_cache)); + + 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; +} + +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; +} + +bool cache_is_cached(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].it_addr == addr); +} + +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; +} + +void cache_insert(PageCache *cache, uint64_t addr, uint8_t *pdata) +{ + + CacheItem *it = NULL; + + g_assert(cache); + g_assert(cache->page_cache); + + /* actual update of entry */ + it = cache_get_by_addr(cache, addr); + + if (!it->it_data) { + cache->num_items++; + } + + it->it_data = pdata; + it->it_age = ++cache->max_item_age; + it->it_addr = addr; +} + +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) { + /* keep the MRU page */ + if (new_it->it_age >= old_it->it_age) { + g_free(old_it->it_data); + } else { + 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; + } + } else { + cache_insert(new_cache, old_it->it_addr, old_it->it_data); + } + } + } + + 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; +} |