[Qemu-devel] [v2 1/4] migration: do cleanup operation after completion

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

Because of the patch 3ea3b7fa9af067982f34b of kvm, now the migration_end()
is a time consuming operation, which takes about dozens of milliseconds, and
will prolong VM downtime. Such an operation should be done after migration
completion.

For a VM with 8G RAM, this patch can reduce the VM downtime about 32 ms during
live migration.

Signed-off-by: Liang Li <liang.z.li@intel.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
---
 migration/block.c     |  1 -
 migration/migration.c | 14 +++++++-------
 migration/ram.c       |  1 -
 3 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/migration/block.c b/migration/block.c
index ed865ed..85496fd 100644
--- a/migration/block.c
+++ b/migration/block.c
@@ -750,7 +750,6 @@ static int block_save_complete(QEMUFile *f, void *opaque)
 
     qemu_put_be64(f, BLK_MIG_FLAG_EOS);
 
-    blk_mig_cleanup();
     return 0;
 }
 
diff --git a/migration/migration.c b/migration/migration.c
index 662e77e..4ddb9ad 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -560,12 +560,9 @@ static void migrate_fd_cleanup(void *opaque)
 
     assert(s->state != MIGRATION_STATUS_ACTIVE);
 
-    if (s->state != MIGRATION_STATUS_COMPLETED) {
-        qemu_savevm_state_cancel();
-        if (s->state == MIGRATION_STATUS_CANCELLING) {
-            migrate_set_state(s, MIGRATION_STATUS_CANCELLING,
-                              MIGRATION_STATUS_CANCELLED);
-        }
+    if (s->state == MIGRATION_STATUS_CANCELLING) {
+        migrate_set_state(s, MIGRATION_STATUS_CANCELLING,
+                          MIGRATION_STATUS_CANCELLED);
     }
 
     notifier_list_notify(&migration_state_notifiers, s);
@@ -923,6 +920,7 @@ static void *migration_thread(void *opaque)
     int64_t initial_bytes = 0;
     int64_t max_size = 0;
     int64_t start_time = initial_time;
+    int64_t end_time;
     bool old_vm_running = false;
 
     rcu_register_thread();
@@ -1007,9 +1005,11 @@ static void *migration_thread(void *opaque)
         }
     }
 
+    end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
+
     qemu_mutex_lock_iothread();
+    qemu_savevm_state_cancel();
     if (s->state == MIGRATION_STATUS_COMPLETED) {
-        int64_t end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
         uint64_t transferred_bytes = qemu_ftell(s->file);
         s->total_time = end_time - s->total_time;
         s->downtime = end_time - start_time;
diff --git a/migration/ram.c b/migration/ram.c
index 7f007e6..6249f6e 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1269,7 +1269,6 @@ static int ram_save_complete(QEMUFile *f, void *opaque)
 
     rcu_read_unlock();
 
-    migration_end();
     qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
 
     return 0;
-- 
1.9.1