diff mbox

[v2,RESEND,1/4] migration: defer migration_end & blk_mig_cleanup

Message ID 1446449823-25049-2-git-send-email-liang.z.li@intel.com
State New
Headers show

Commit Message

Li, Liang Z Nov. 2, 2015, 7:37 a.m. UTC 
Because of the patch 3ea3b7fa9af067982f34b of kvm, which introduces a
lazy collapsing of small sptes into large sptes mechanism, now
migration_end() is a time consuming operation because it calls
memroy_global_dirty_log_stop(), which will trigger the dropping of small
sptes operation and takes about dozens of milliseconds, so call
migration_end() before all the vmsate data has already been transferred
to the destination will prolong VM downtime. This operation should be
deferred after all the data has been transferred to the destination.

blk_mig_cleanup() can be deferred too.

For a VM with 8G RAM, this patch can reduce the VM downtime about 30 ms.

Signed-off-by: Liang Li <liang.z.li@intel.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
---
 migration/block.c     |  1 -
 migration/migration.c | 13 ++++++-------
 migration/ram.c       |  1 -
 3 files changed, 6 insertions(+), 9 deletions(-)

Comments

Juan Quintela Nov. 3, 2015, 12:28 p.m. UTC | #1 
Liang Li <liang.z.li@intel.com> wrote:
> Because of the patch 3ea3b7fa9af067982f34b of kvm, which introduces a
> lazy collapsing of small sptes into large sptes mechanism, now
> migration_end() is a time consuming operation because it calls
> memroy_global_dirty_log_stop(), which will trigger the dropping of small
> sptes operation and takes about dozens of milliseconds, so call
> migration_end() before all the vmsate data has already been transferred
> to the destination will prolong VM downtime. This operation should be
> deferred after all the data has been transferred to the destination.
>
> blk_mig_cleanup() can be deferred too.
>
> For a VM with 8G RAM, this patch can reduce the VM downtime about 30 ms.
>
> Signed-off-by: Liang Li <liang.z.li@intel.com>
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

And the naming makes more sense even, thanks
diff mbox

Patch

diff --git a/migration/block.c b/migration/block.c
index f7bb1e0..8401597 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 b092f38..d5a7304 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -613,12 +613,9 @@  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);
@@ -1028,6 +1025,7 @@  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();
@@ -1089,10 +1087,11 @@  static void *migration_thread(void *opaque)
 
     /* If we enabled cpu throttling for auto-converge, turn it off. */
     cpu_throttle_stop();
+    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 a25bcc7..25e9eeb 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1344,7 +1344,6 @@  static int ram_save_complete(QEMUFile *f, void *opaque)
 
     rcu_read_unlock();
 
-    migration_end();
     qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
 
     return 0;