Add LRU page cache mechanism.
The page are accessed by their address.
Signed-off-by: Benoit Hudzia <benoit.hud...@sap.com>
Signed-off-by: Petter Svard <pett...@cs.umu.se>
Signed-off-by: Aidan Shribman <aidan.shrib...@sap.com>
Signed-off-by: Orit Wasserman <owass...@redhat.com>
---
Makefile.objs | 1 +
cache.c | 217 ++++++++++++++++++++++++++++++++++++++++++++++++++
include/qemu/cache.h | 79 ++++++++++++++++++
qemu-common.h | 10 +++
4 files changed, 307 insertions(+), 0 deletions(-)
create mode 100644 cache.c
create mode 100644 include/qemu/cache.h
diff --git a/Makefile.objs b/Makefile.objs
index 625c4d5..d9c6859 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -77,6 +77,7 @@ common-obj-y += qemu-char.o #aio.o
common-obj-y += block-migration.o iohandler.o
common-obj-y += pflib.o
common-obj-y += bitmap.o bitops.o
+common-obj-y += cache.o
common-obj-$(CONFIG_POSIX) += migration-exec.o migration-unix.o migration-fd.o
common-obj-$(CONFIG_WIN32) += version.o
diff --git a/cache.c b/cache.c
new file mode 100644
index 0000000..729fc64
--- /dev/null
+++ b/cache.c
@@ -0,0 +1,217 @@
+/*
+ * Page cache for qemu
+ * The cache is base on a hash on the page address
+ *
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Orit Wasserman <owass...@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/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;
+ unsigned long it_age;
+ uint8_t *it_data;
+};
+
+struct Cache {
+ CacheItem *page_cache;
+ unsigned int page_size;
+ int64_t max_num_items;
+ uint64_t max_item_age;
+ int64_t num_items;
+};
+
+Cache *cache_init(int64_t num_pages, unsigned int page_size)
+{
+ int i;
+
+ Cache *cache = g_malloc(sizeof(Cache));
+ if (!cache) {
+ DPRINTF("Error allocation Cache\n");
+ return NULL;
+ }
+
+ if (num_pages <= 0) {
+ DPRINTF("invalid number pages\n");
+ return NULL;
+ }
+
+ /* round down to the nearest power of 2 */
+ if (!is_power_of_2(num_pages)) {
+ num_pages = 1 << ffs(num_pages);
+ DPRINTF("rounding down to %ld\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 %lu\n", cache->max_num_items);
+
+ cache->page_cache = g_malloc((cache->max_num_items) *
+ sizeof(CacheItem));
+ if (!cache->page_cache) {
+ DPRINTF("could not allocate 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(Cache *cache)
+{
+ int 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);
+ cache->page_cache[i].it_data = 0;
+ }
+
+ g_free(cache->page_cache);
+ cache->page_cache = NULL;
+}
+
+static unsigned long cache_get_cache_pos(const Cache *cache, uint64_t address)
+{
+ unsigned long pos;
+
+ g_assert(cache->max_num_items);
+ pos = (address/cache->page_size) & (cache->max_num_items - 1);
+ return pos;
+}
+
+bool cache_is_cached(const Cache *cache, uint64_t addr)
+{
+ unsigned long 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 Cache *cache, uint64_t addr)
+{
+ unsigned long 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 Cache *cache, uint64_t addr)
+{
+ return cache_get_by_addr(cache, addr)->it_data;
+}
+
+void cache_insert(Cache *cache, unsigned long 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;
+}
+
+int cache_resize(Cache *cache, int64_t new_num_pages)
+{
+ Cache *new_cache;
+ int i;
+
+ CacheItem *old_it, *new_it;
+
+ g_assert(cache);
+
+ /* same size */
+ if (new_num_pages == cache->max_num_items) {
+ return 0;
+ }
+
+ /* cache was not inited */
+ if (cache->page_cache == NULL) {
+ return -1;
+ }
+
+ 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 the first value */
+ new_it = cache_get_by_addr(new_cache, old_it->it_addr);
+ if (new_it->it_data) {
+ g_free(old_it->it_data);
+ } 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 0;
+}
diff --git a/include/qemu/cache.h b/include/qemu/cache.h
new file mode 100644
index 0000000..9ca2d0a
--- /dev/null
+++ b/include/qemu/cache.h
@@ -0,0 +1,79 @@
+/*
+ * Page cache for qemu
+ * The cache is base on a hash on the page address
+ *
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Orit Wasserman <owass...@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.
+ *
+ */
+
+#ifndef CACHE_H
+#define CACHE_H
+
+/* Page cache for storing guest pages */
+typedef struct Cache Cache;
+
+/**
+ * cache_init: Initialize the page cache
+ *
+ *
+ * Returns new allocated cache or NULL on error
+ *
+ * @cache pointer to the Cache struct
+ * @num_pages: cache maximal number of cached pages
+ * @page_size: cache page size
+ */
+Cache *cache_init(int64_t num_pages, unsigned int page_size);
+
+/**
+ * cache_fini: free all cache resources
+ * @cache pointer to the Cache struct
+ */
+void cache_fini(Cache *cache);
+
+/**
+ * cache_is_cached: Checks to see if the page is cached
+ *
+ * Returns %true if page is cached
+ *
+ * @cache pointer to the Cache struct
+ * @addr: page addr
+ */
+bool cache_is_cached(const Cache *cache, uint64_t addr);
+
+/**
+ * get_cached_data: Get the data cached for an addr
+ *
+ * Returns pointer to the data cached or NULL if not cached
+ *
+ * @cache pointer to the Cache struct
+ * @addr: page addr
+ */
+uint8_t *get_cached_data(const Cache *cache, uint64_t addr);
+
+/**
+ * cache_insert: insert the page into the cache. the previous value will be
overwritten
+ *
+ * @cache pointer to the Cache struct
+ * @addr: page address
+ * @pdata: pointer to the page
+ */
+void cache_insert(Cache *cache, uint64_t addr, uint8_t *pdata);
+
+/**
+ * cache_resize: resize the page cache. In case of size reduction the extra
pages
+ * will be freed
+ *
+ * Returns -1 on error
+ *
+ * @cache pointer to the Cache struct
+ * @num_pages: new page cache size (in pages)
+ */
+int cache_resize(Cache *cache, int64_t num_pages);
+
+#endif
diff --git a/qemu-common.h b/qemu-common.h
index c8c6b2a..45b1d97 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -1,3 +1,4 @@
+
/* Common header file that is included by all of qemu. */
#ifndef QEMU_COMMON_H
#define QEMU_COMMON_H
@@ -417,6 +418,15 @@ static inline uint64_t muldiv64(uint64_t a, uint32_t b,
uint32_t c)
/* Round number up to multiple */
#define QEMU_ALIGN_UP(n, m) QEMU_ALIGN_DOWN((n) + (m) - 1, (m))
+static inline bool is_power_of_2(int64_t value)
+{
+ if (!value) {
+ return 0;
+ }
+
+ return !(value & (value - 1));
+}
+
#include "module.h"
#endif
--
1.7.7.6
