[Qemu-devel] [v4 09/13] migration: Make compression co-work with xbzrle

[Liang Li <liang.z.li@intel.com>]

Now, multiple thread compression can co-work with xbzrle. when
xbzrle is on, multiple thread compression will only work at the
first round of RAM data sync.

Signed-off-by: Liang Li <liang.z.li@intel.com>
Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
---
 arch_init.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch_init.c b/arch_init.c
index b8bdb16..8ef0315 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -364,6 +364,7 @@ static QemuCond *comp_done_cond;
 /* The empty QEMUFileOps will be used by file in CompressParam */
 static const QEMUFileOps empty_ops = { };
 static bool quit_thread;
+static bool compression_switch_on;
 static int one_byte_count;
 static DecompressParam *decomp_param;
 static QemuThread *decompress_threads;
@@ -440,6 +441,7 @@ void migrate_compress_threads_create(MigrationState *s)
         return;
     }
     quit_thread = false;
+    compression_switch_on = true;
     thread_count = migrate_compress_threads();
     s->compress_thread = g_new0(QemuThread, thread_count);
     comp_param = g_new0(CompressParam, thread_count);
@@ -957,9 +959,16 @@ static int ram_find_and_save_block(QEMUFile *f, bool last_stage)
                 block = QTAILQ_FIRST(&ram_list.blocks);
                 complete_round = true;
                 ram_bulk_stage = false;
+                if (migrate_use_xbzrle()) {
+                    /* If xbzrle is on, stop using the data compression at this
+                     * point. In theory, xbzrle can do better than compression.
+                     */
+                    flush_compressed_data(f);
+                    compression_switch_on = false;
+                }
             }
         } else {
-            if (migrate_use_compression()) {
+            if (compression_switch_on && migrate_use_compression()) {
                 bytes_sent = ram_save_compressed_page(f, block, offset,
                                                       last_stage);
             } else {
-- 
1.9.1