Re: [Qemu-devel] [PATCH 12/41] migration: do not nest flushing of device data

[Orit Wasserman]

On 02/15/2013 07:46 PM, Paolo Bonzini wrote:
> Completion of migration is currently done with a "nested" loop that
> invokes buffered_flush: migrate_fd_completed is called by
> buffered_file_thread, which calls migrate_fd_cleanup, which calls
> buffered_close (via qemu_fclose), which flushes the buffer.
> 
> Simplify this, by reusing the buffered_flush call of buffered_file_thread.
> Then if qemu_savevm_state_complete was called, and the buffer is empty
> (including the QEMUFile buffer, for which we need the previous patch), we
> are done.
> 
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  migration.c |   55 ++++++++++++++++++++++++-------------------------------
>  1 files changed, 24 insertions(+), 31 deletions(-)
> 
> diff --git a/migration.c b/migration.c
> index 75dd38a..b0b5578 100644
> --- a/migration.c
> +++ b/migration.c
> @@ -262,41 +262,34 @@ void 
> qmp_migrate_set_capabilities(MigrationCapabilityStatusList *params,
>  
>  static void migrate_fd_cleanup(MigrationState *s)
>  {
> -    int ret = 0;
> -
>      if (s->file) {
>          DPRINTF("closing file\n");
> -        ret = qemu_fclose(s->file);
> +        qemu_fclose(s->file);
>          s->file = NULL;
>      }
>  
>      assert(s->fd == -1);
> -    if (ret < 0 && s->state == MIG_STATE_ACTIVE) {
> -        s->state = MIG_STATE_ERROR;
> -    }
> +    assert(s->state != MIG_STATE_ACTIVE);
>  
> -    if (s->state != MIG_STATE_ACTIVE) {
> +    if (s->state != MIG_STATE_COMPLETED) {
>          qemu_savevm_state_cancel();
>      }
> +
> +    notifier_list_notify(&migration_state_notifiers, s);
>  }
>  
>  void migrate_fd_error(MigrationState *s)
>  {
>      DPRINTF("setting error state\n");
>      s->state = MIG_STATE_ERROR;
> -    notifier_list_notify(&migration_state_notifiers, s);
>      migrate_fd_cleanup(s);
>  }
>  
>  static void migrate_fd_completed(MigrationState *s)
>  {
>      DPRINTF("setting completed state\n");
> +    s->state = MIG_STATE_COMPLETED;
>      migrate_fd_cleanup(s);
> -    if (s->state == MIG_STATE_ACTIVE) {
> -        s->state = MIG_STATE_COMPLETED;
> -        runstate_set(RUN_STATE_POSTMIGRATE);
> -    }
> -    notifier_list_notify(&migration_state_notifiers, s);
>  }
>  
>  static ssize_t migrate_fd_put_buffer(MigrationState *s, const void *data,
> @@ -326,8 +319,6 @@ static void migrate_fd_cancel(MigrationState *s)
>      DPRINTF("cancelling migration\n");
>  
>      s->state = MIG_STATE_CANCELLED;
> -    notifier_list_notify(&migration_state_notifiers, s);
> -
>      migrate_fd_cleanup(s);
>  }
>  
> @@ -592,10 +583,6 @@ static int buffered_close(void *opaque)
>  
>      DPRINTF("closing\n");
>  
> -    s->xfer_limit = INT_MAX;
> -    while (!qemu_file_get_error(s->file) && s->buffer_size) {
> -        buffered_flush(s);
> -    }
>      return migrate_fd_close(s);
>  }
>  
> @@ -657,6 +644,8 @@ static void *buffered_file_thread(void *opaque)
>      MigrationState *s = opaque;
>      int64_t initial_time = qemu_get_clock_ms(rt_clock);
>      int64_t max_size = 0;
> +    int64_t start_time = initial_time;
> +    bool old_vm_running = false;
>      bool last_round = false;
>  
>      qemu_mutex_lock_iothread();
> @@ -674,23 +663,13 @@ static void *buffered_file_thread(void *opaque)
>              if (pending_size && pending_size >= max_size) {
>                  qemu_savevm_state_iterate(s->file);
>              } else {
> -                int old_vm_running = runstate_is_running();
> -                int64_t start_time, end_time;
> -
>                  DPRINTF("done iterating\n");
>                  start_time = qemu_get_clock_ms(rt_clock);
>                  qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
> +                old_vm_running = runstate_is_running();
>                  vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
> +                s->xfer_limit = INT_MAX;
>                  qemu_savevm_state_complete(s->file);
> -                migrate_fd_completed(s);
> -                end_time = qemu_get_clock_ms(rt_clock);
> -                s->total_time = end_time - s->total_time;
> -                s->downtime = end_time - start_time;
> -                if (s->state != MIG_STATE_COMPLETED) {
> -                    if (old_vm_running) {
> -                        vm_start();
> -                    }
> -                }
>                  last_round = true;
>              }
>          }
> @@ -716,6 +695,20 @@ static void *buffered_file_thread(void *opaque)
>          qemu_mutex_lock_iothread();
>          if (qemu_file_get_error(s->file)) {
>              migrate_fd_error(s);
> +        } else if (last_round && s->buffer_size == 0) {
> +            migrate_fd_completed(s);
> +        }
> +    }
> +
> +    if (s->state == MIG_STATE_COMPLETED) {
> +        int64_t end_time = qemu_get_clock_ms(rt_clock);
> +        s->total_time = end_time - s->total_time;
> +        s->downtime = end_time - start_time;
> +        runstate_set(RUN_STATE_POSTMIGRATE);
> +    } else {
> +        if (old_vm_running) {
> +            assert(last_round);
> +            vm_start();
>          }
>      }
>  
> 
Reviewed-by: Orit Wasserman <address@hidden>