[Qemu-devel] [PATCH v11 4/9] Add cache handling functions

[Orit Wasserman <owasserm@redhat.com>]

Add LRU page cache mechanism.
The page are accessed by their address.

Signed-off-by: Benoit Hudzia <benoit.hudzia@sap.com>
Signed-off-by: Petter Svard <petters@cs.umu.se>
Signed-off-by: Aidan Shribman <aidan.shribman@sap.com>
Signed-off-by: Orit Wasserman <owasserm@redhat.com>
---
 Makefile.objs        |    1 +
 cache.c              |  219 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/qemu/cache.h |   81 ++++++++++++++++++
 qemu-common.h        |   10 +++
 4 files changed, 311 insertions(+), 0 deletions(-)
 create mode 100644 cache.c
 create mode 100644 include/qemu/cache.h

diff --git a/Makefile.objs b/Makefile.objs
index 70c5c79..8fed055 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -137,6 +137,7 @@ common-obj-y += qdev.o qdev-properties.o qdev-monitor.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-$(CONFIG_BRLAPI) += baum.o
 common-obj-$(CONFIG_POSIX) += migration-exec.o migration-unix.o migration-fd.o
diff --git a/cache.c b/cache.c
new file mode 100644
index 0000000..cc0870b
--- /dev/null
+++ b/cache.c
@@ -0,0 +1,219 @@
+/*
+ * Page cache for qemu
+ * The cache is base on a hash on the page address
+ *
+ * Copyright 2011 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.  See
+ * the COPYING file in the top-level directory.
+ *
+ * Contributions after 2012-01-13 are licensed under the terms of the
+ * GNU GPL, version 2 or (at your option) any later version.
+ */
+
+#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 nearst 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..16145e1
--- /dev/null
+++ b/include/qemu/cache.h
@@ -0,0 +1,81 @@
+/*
+ * Page cache for qemu
+ * The cache is base on a hash on the page address
+ *
+ * Copyright 2011 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.  See
+ * the COPYING file in the top-level directory.
+ *
+ * Contributions after 2012-01-13 are licensed under the terms of the
+ * GNU GPL, version 2 or (at your option) any later version.
+ */
+
+#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 231c012..83571e0 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
@@ -408,6 +409,15 @@ 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