[Qemu-devel] [PATCH v6 01/11] Add cache handling functions

[Orit Wasserman <owasserm@redhat.com>]

Add LRU page caching mechanism.
The pages are stored in the cache ordered by their address.

Signed-off-by: Orit Wasserman <owasserm@redhat.com>
---
 arch_init.c |  175 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 175 insertions(+), 0 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 95ac682..34e4e60 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -28,6 +28,7 @@
 #include <sys/types.h>
 #include <sys/mman.h>
 #endif
+#include <assert.h>
 #include "config.h"
 #include "monitor.h"
 #include "sysemu.h"
@@ -43,6 +44,14 @@
 #include "hw/smbios.h"
 #include "exec-memory.h"
 
+#ifdef DEBUG_ARCH_INIT
+#define DPRINTF(fmt, ...) \
+    do { fprintf(stdout, "arch_init: " fmt, ## __VA_ARGS__); } while (0)
+#else
+#define DPRINTF(fmt, ...) \
+    do { } while (0)
+#endif
+
 #ifdef TARGET_SPARC
 int graphic_width = 1024;
 int graphic_height = 768;
@@ -126,6 +135,172 @@ static int is_dup_page(uint8_t *page)
     return 1;
 }
 
+/***********************************************************/
+/* Page cache for storing previous pages as basis for XBZRLE compression */
+#define CACHE_N_WAY 2 /* 2-way assossiative cache */
+
+typedef struct CacheItem {
+    ram_addr_t it_addr;
+    unsigned long it_age;
+    uint8_t *it_data;
+} CacheItem;
+
+typedef struct CacheBucket {
+    CacheItem bkt_item[CACHE_N_WAY];
+} CacheBucket;
+
+static CacheBucket *page_cache;
+static int64_t cache_num_buckets;
+static uint64_t cache_max_item_age;
+static int64_t cache_num_items;
+
+static void cache_init(ssize_t num_buckets);
+static void cache_fini(void);
+static int cache_is_cached(ram_addr_t addr);
+static int cache_get_oldest(CacheBucket *buck);
+static int cache_get_newest(CacheBucket *buck, ram_addr_t addr);
+static void cache_insert(ram_addr_t id, uint8_t *pdata);
+static unsigned long cache_get_cache_pos(ram_addr_t address);
+static CacheItem *cache_item_get(unsigned long pos, int item);
+
+/***********************************************************/
+/* XBRLE page cache implementation */
+static CacheItem *cache_item_get(unsigned long pos, int item)
+{
+    assert(page_cache);
+    return &page_cache[pos].bkt_item[item];
+}
+
+static void cache_init(int64_t num_bytes)
+{
+    int i;
+
+    cache_num_items = 0;
+    cache_max_item_age = 0;
+    cache_num_buckets = num_bytes / (TARGET_PAGE_SIZE * CACHE_N_WAY);
+    assert(cache_num_buckets);
+    DPRINTF("Setting cache buckets to %lu\n", cache_num_buckets);
+
+    assert(!page_cache);
+    page_cache = (CacheBucket *)g_malloc((cache_num_buckets) *
+            sizeof(CacheBucket));
+
+    for (i = 0; i < cache_num_buckets; i++) {
+        int j;
+        for (j = 0; j < CACHE_N_WAY; j++) {
+            CacheItem *it = cache_item_get(i, j);
+            it->it_data = NULL;
+            it->it_age = 0;
+            it->it_addr = -1;
+        }
+    }
+}
+
+static void cache_fini(void)
+{
+    int i;
+
+    assert(page_cache);
+
+    for (i = 0; i < cache_num_buckets; i++) {
+        int j;
+        for (j = 0; j < CACHE_N_WAY; j++) {
+            CacheItem *it = cache_item_get(i, j);
+            g_free(it->it_data);
+            it->it_data = 0;
+        }
+    }
+
+    g_free(page_cache);
+    page_cache = NULL;
+}
+
+static unsigned long cache_get_cache_pos(ram_addr_t address)
+{
+    unsigned long pos;
+
+    assert(cache_num_buckets);
+    pos = (address/TARGET_PAGE_SIZE) & (cache_num_buckets - 1);
+    return pos;
+}
+
+static int cache_get_newest(CacheBucket *buck, ram_addr_t addr)
+{
+    unsigned long big = 0;
+    int big_pos = -1;
+    int j;
+
+    assert(page_cache);
+
+    for (j = 0; j < CACHE_N_WAY; j++) {
+        CacheItem *it = &buck->bkt_item[j];
+
+        if (it->it_addr != addr) {
+            continue;
+        }
+
+        if (!j || it->it_age > big) {
+            big = it->it_age;
+            big_pos = j;
+        }
+    }
+
+    return big_pos;
+}
+
+static int cache_get_oldest(CacheBucket *buck)
+{
+    unsigned long small = 0;
+    int small_pos = -1;
+    int j;
+
+    assert(page_cache);
+
+    for (j = 0; j < CACHE_N_WAY; j++) {
+        CacheItem *it = &buck->bkt_item[j];
+
+        if (!j || it->it_age <  small) {
+            small = it->it_age;
+            small_pos = j;
+        }
+    }
+
+    return small_pos;
+}
+
+static int cache_is_cached(ram_addr_t addr)
+{
+    unsigned long pos = cache_get_cache_pos(addr);
+
+    assert(page_cache);
+    CacheBucket *bucket = &page_cache[pos];
+    return cache_get_newest(bucket, addr);
+}
+
+static void cache_insert(unsigned long addr, uint8_t *pdata)
+{
+    unsigned long pos;
+    int slot = -1;
+    CacheBucket *bucket;
+
+    pos = cache_get_cache_pos(addr);
+    assert(page_cache);
+    bucket = &page_cache[pos];
+    slot = cache_get_oldest(bucket); /* evict LRU */
+
+    /* actual update of entry */
+    CacheItem *it = cache_item_get(pos, slot);
+    if (!it->it_data) {
+        it->it_data = g_malloc(TARGET_PAGE_SIZE);
+        cache_num_items++;
+    }
+
+    memcpy(it->it_data, pdata, TARGET_PAGE_SIZE);
+    it->it_age = ++cache_max_item_age;
+    it->it_addr = addr;
+}
+
+
 static RAMBlock *last_block;
 static ram_addr_t last_offset;
 
-- 
1.7.6.5