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