Patchwork [19/22] Add XBZRLE to ram_save_block and ram_save_live

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Submitter Juan Quintela
Date July 13, 2012, 7:23 a.m.
Message ID <1342164224-32709-20-git-send-email-quintela@redhat.com>
Download mbox | patch
Permalink /patch/170822/
State New
Headers show

Comments

Juan Quintela - July 13, 2012, 7:23 a.m.
From: Orit Wasserman <owasserm@redhat.com>

In the outgoing migration check to see if the page is cached and
changed than send compressed page by using save_xbrle_page function.
In the incoming migration check to see if RAM_SAVE_FLAG_XBZRLE is set
and decompress the page (by using load_xbrle function).

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>
Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 arch_init.c |  169 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 migration.c |   24 +++++++++
 migration.h |    4 ++
 3 files changed, 194 insertions(+), 3 deletions(-)

Patch

diff --git a/arch_init.c b/arch_init.c
index 78cdf50..a3a4707 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -43,6 +43,7 @@ 
 #include "hw/smbios.h"
 #include "exec-memory.h"
 #include "hw/pcspk.h"
+#include "qemu/page_cache.h"

 #ifdef DEBUG_ARCH_INIT
 #define DPRINTF(fmt, ...) \
@@ -102,6 +103,7 @@  const uint32_t arch_type = QEMU_ARCH;
 #define RAM_SAVE_FLAG_PAGE     0x08
 #define RAM_SAVE_FLAG_EOS      0x10
 #define RAM_SAVE_FLAG_CONTINUE 0x20
+#define RAM_SAVE_FLAG_XBZRLE   0x40

 #ifdef __ALTIVEC__
 #include <altivec.h>
@@ -169,6 +171,27 @@  static int is_dup_page(uint8_t *page)
     return 1;
 }

+/* XBZRLE (Xor Based Zero Length Encoding */
+typedef struct XBZRLEHeader {
+    uint16_t xh_len;
+    uint8_t xh_flags;
+} XBZRLEHeader;
+
+/* struct contains XBZRLE cache and a static page
+   used by the compression */
+static struct {
+    /* buffer used for XBZRLE encoding */
+    uint8_t *encoded_buf;
+    /* buffer used for XBZRLE decoding */
+    uint8_t *decoded_buf;
+    /* Cache for XBZRLE */
+    PageCache *cache;
+} XBZRLE = {
+    .encoded_buf = NULL,
+    .decoded_buf = NULL,
+    .cache = NULL,
+};
+
 static void save_block_hdr(QEMUFile *f, RAMBlock *block, ram_addr_t offset,
         int cont, int flag)
 {
@@ -181,6 +204,60 @@  static void save_block_hdr(QEMUFile *f, RAMBlock *block, ram_addr_t offset,

 }

+#define ENCODING_FLAG_XBZRLE 0x1
+
+static int save_xbzrle_page(QEMUFile *f, uint8_t *current_data,
+                            ram_addr_t current_addr, RAMBlock *block,
+                            ram_addr_t offset, int cont)
+{
+    int encoded_len = 0, bytes_sent = -1, ret = -1;
+    XBZRLEHeader hdr = {
+        .xh_len = 0,
+        .xh_flags = 0,
+    };
+    uint8_t *prev_cached_page;
+
+    if (!cache_is_cached(XBZRLE.cache, current_addr)) {
+        cache_insert(XBZRLE.cache, current_addr,
+                     g_memdup(current_data, TARGET_PAGE_SIZE));
+        return -1;
+    }
+
+    prev_cached_page = get_cached_data(XBZRLE.cache, current_addr);
+
+    /* XBZRLE encoding (if there is no overflow) */
+    encoded_len = xbzrle_encode_buffer(prev_cached_page, current_data,
+                                       TARGET_PAGE_SIZE, XBZRLE.encoded_buf,
+                                       TARGET_PAGE_SIZE);
+    if (encoded_len == 0) {
+        DPRINTF("Skipping unmodified page\n");
+        return 0;
+    } else if (encoded_len == -1) {
+        DPRINTF("Overflow\n");
+        /* update data in the cache */
+        memcpy(prev_cached_page, current_data, TARGET_PAGE_SIZE);
+        return -1;
+    }
+
+    /* we need to update the data in the cache, in order to get the same data
+       we cached we decode the encoded page on the cached data */
+    ret = xbzrle_decode_buffer(XBZRLE.encoded_buf, encoded_len,
+                               prev_cached_page, TARGET_PAGE_SIZE);
+    g_assert(ret != -1);
+
+    hdr.xh_len = encoded_len;
+    hdr.xh_flags |= ENCODING_FLAG_XBZRLE;
+
+    /* Send XBZRLE based compressed page */
+    save_block_hdr(f, block, offset, cont, RAM_SAVE_FLAG_XBZRLE);
+    qemu_put_byte(f, hdr.xh_flags);
+    qemu_put_be16(f, hdr.xh_len);
+    qemu_put_buffer(f, XBZRLE.encoded_buf, encoded_len);
+    bytes_sent = encoded_len + sizeof(hdr);
+
+    return bytes_sent;
+}
+
 static RAMBlock *last_block;
 static ram_addr_t last_offset;

@@ -198,6 +275,7 @@  static int ram_save_block(QEMUFile *f)
     ram_addr_t offset = last_offset;
     int bytes_sent = -1;
     MemoryRegion *mr;
+    ram_addr_t current_addr;

     if (!block)
         block = QLIST_FIRST(&ram_list.blocks);
@@ -218,13 +296,24 @@  static int ram_save_block(QEMUFile *f)
                 save_block_hdr(f, block, offset, cont, RAM_SAVE_FLAG_COMPRESS);
                 qemu_put_byte(f, *p);
                 bytes_sent = 1;
-            } else {
+            } else if (migrate_use_xbzrle()) {
+                current_addr = block->offset + offset;
+                bytes_sent = save_xbzrle_page(f, p, current_addr, block,
+                                              offset, cont);
+                p = get_cached_data(XBZRLE.cache, current_addr);
+            }
+
+            /* either we didn't send yet (we may have had XBZRLE overflow) */
+            if (bytes_sent == -1) {
                 save_block_hdr(f, block, offset, cont, RAM_SAVE_FLAG_PAGE);
                 qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
                 bytes_sent = TARGET_PAGE_SIZE;
             }

-            break;
+            /* if page is unmodified, continue to the next */
+            if (bytes_sent != 0) {
+                break;
+            }
         }

         offset += TARGET_PAGE_SIZE;
@@ -302,6 +391,14 @@  static void sort_ram_list(void)
 static void migration_end(void)
 {
     memory_global_dirty_log_stop();
+
+    if (migrate_use_xbzrle()) {
+        cache_fini(XBZRLE.cache);
+        g_free(XBZRLE.cache);
+        g_free(XBZRLE.encoded_buf);
+        g_free(XBZRLE.decoded_buf);
+        XBZRLE.cache = NULL;
+    }
 }

 static void ram_migration_cancel(void *opaque)
@@ -321,7 +418,17 @@  static int ram_save_setup(QEMUFile *f, void *opaque)
     last_offset = 0;
     sort_ram_list();

-    /* Make sure all dirty bits are set */
+    if (migrate_use_xbzrle()) {
+        XBZRLE.cache = cache_init(migrate_xbzrle_cache_size() /
+                                  TARGET_PAGE_SIZE,
+                                  TARGET_PAGE_SIZE);
+        if (!XBZRLE.cache) {
+            DPRINTF("Error creating cache\n");
+            return -1;
+        }
+        XBZRLE.encoded_buf = g_malloc0(TARGET_PAGE_SIZE);
+    }
+
     QLIST_FOREACH(block, &ram_list.blocks, next) {
         for (addr = 0; addr < block->length; addr += TARGET_PAGE_SIZE) {
             if (!memory_region_get_dirty(block->mr, addr, TARGET_PAGE_SIZE,
@@ -436,6 +543,49 @@  static int ram_save_complete(QEMUFile *f, void *opaque)
     return 0;
 }

+static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host)
+{
+    int ret, rc = 0;
+    XBZRLEHeader hdr = {
+        .xh_len = 0,
+        .xh_flags = 0,
+    };
+
+    if (!XBZRLE.decoded_buf) {
+        XBZRLE.decoded_buf = g_malloc(TARGET_PAGE_SIZE);
+    }
+
+    /* extract RLE header */
+    hdr.xh_flags = qemu_get_byte(f);
+    hdr.xh_len = qemu_get_be16(f);
+
+    if (!(hdr.xh_flags & ENCODING_FLAG_XBZRLE)) {
+        fprintf(stderr, "Failed to load XBZRLE page - wrong compression!\n");
+        return -1;
+    }
+
+    if (hdr.xh_len > TARGET_PAGE_SIZE) {
+        fprintf(stderr, "Failed to load XBZRLE page - len overflow!\n");
+        return -1;
+    }
+    /* load data and decode */
+    qemu_get_buffer(f, XBZRLE.decoded_buf, hdr.xh_len);
+
+    /* decode RLE */
+    ret = xbzrle_decode_buffer(XBZRLE.decoded_buf, hdr.xh_len, host,
+                               TARGET_PAGE_SIZE);
+    if (ret == -1) {
+        fprintf(stderr, "Failed to load XBZRLE page - decode error!\n");
+        rc = -1;
+    } else  if (ret > TARGET_PAGE_SIZE) {
+        fprintf(stderr, "Failed to load XBZRLE page - size %d exceeds %d!\n",
+                ret, TARGET_PAGE_SIZE);
+        rc = -1;
+    }
+
+    return rc;
+}
+
 static inline void *host_from_stream_offset(QEMUFile *f,
                                             ram_addr_t offset,
                                             int flags)
@@ -549,6 +699,19 @@  static int ram_load(QEMUFile *f, void *opaque, int version_id)
             }

             qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
+        } else if (flags & RAM_SAVE_FLAG_XBZRLE) {
+            if (!migrate_use_xbzrle()) {
+                return -EINVAL;
+            }
+            void *host = host_from_stream_offset(f, addr, flags);
+            if (!host) {
+                return -EINVAL;
+            }
+
+            if (load_xbzrle(f, addr, host) < 0) {
+                ret = -EINVAL;
+                goto done;
+            }
         }
         error = qemu_file_get_error(f);
         if (error) {
diff --git a/migration.c b/migration.c
index fd004d7..1a264a9 100644
--- a/migration.c
+++ b/migration.c
@@ -43,6 +43,9 @@  enum {

 #define MAX_THROTTLE  (32 << 20)      /* Migration speed throttling */

+/* Migration XBZRLE default cache size */
+#define DEFAULT_MIGRATE_CACHE_SIZE (64 * 1024 * 1024)
+
 static NotifierList migration_state_notifiers =
     NOTIFIER_LIST_INITIALIZER(migration_state_notifiers);

@@ -55,6 +58,7 @@  static MigrationState *migrate_get_current(void)
     static MigrationState current_migration = {
         .state = MIG_STATE_SETUP,
         .bandwidth_limit = MAX_THROTTLE,
+        .xbzrle_cache_size = DEFAULT_MIGRATE_CACHE_SIZE,
     };

     return &current_migration;
@@ -439,6 +443,7 @@  static MigrationState *migrate_init(const MigrationParams *params)
     MigrationState *s = migrate_get_current();
     int64_t bandwidth_limit = s->bandwidth_limit;
     bool enabled_capabilities[MIGRATION_CAPABILITY_MAX];
+    int64_t xbzrle_cache_size = s->xbzrle_cache_size;

     memcpy(enabled_capabilities, s->enabled_capabilities,
            sizeof(enabled_capabilities));
@@ -448,6 +453,7 @@  static MigrationState *migrate_init(const MigrationParams *params)
     s->params = *params;
     memcpy(s->enabled_capabilities, enabled_capabilities,
            sizeof(enabled_capabilities));
+    s->xbzrle_cache_size = xbzrle_cache_size;

     s->state = MIG_STATE_SETUP;
     s->total_time = qemu_get_clock_ms(rt_clock);
@@ -546,3 +552,21 @@  void qmp_migrate_set_downtime(double value, Error **errp)
     value = MAX(0, MIN(UINT64_MAX, value));
     max_downtime = (uint64_t)value;
 }
+
+int migrate_use_xbzrle(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->enabled_capabilities[MIGRATION_CAPABILITY_XBZRLE];
+}
+
+int64_t migrate_xbzrle_cache_size(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->xbzrle_cache_size;
+}
diff --git a/migration.h b/migration.h
index 743c366..cdf6787 100644
--- a/migration.h
+++ b/migration.h
@@ -41,6 +41,7 @@  struct MigrationState
     MigrationParams params;
     int64_t total_time;
     bool enabled_capabilities[MIGRATION_CAPABILITY_MAX];
+    int64_t xbzrle_cache_size;
 };

 void process_incoming_migration(QEMUFile *f);
@@ -104,4 +105,7 @@  int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen,
                          uint8_t *dst, int dlen);
 int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen);

+int migrate_use_xbzrle(void);
+int64_t migrate_xbzrle_cache_size(void);
+
 #endif