Re: [Qemu-devel] [PATCH v7 29/42] Postcopy end in migration_thread

[Dr. David Alan Gilbert]

* Juan Quintela (address@hidden) wrote:
> "Dr. David Alan Gilbert (git)" <address@hidden> wrote:
> > From: "Dr. David Alan Gilbert" <address@hidden>
> >
> > The end of migration in postcopy is a bit different since some of
> > the things normally done at the end of migration have already been
> > done on the transition to postcopy.
> >
> > The end of migration code is getting a bit complciated now, so
> > move out into its own function.
> >
> > Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> 
> I think that I would splint the function and then add the postcopy code.

Done; I now have two patches:
  Split out end of migration code from migration_thread
  Postcopy: End of iteration

> BTW, it is a local function, we can use shorter names:
> 
> migration_completion()?
> 
> trace names specifically get hugggggggggge.

Done.

> > +static void migration_thread_end_of_iteration(MigrationState *s,
> > +                                              int current_active_state,
> 
> RunState?
> And it is not needed as parameter.

No, it's not RunState, it's derived from s->state  which is still an int;
it's also not the current state, but the current state we're expecting
to be in, i.e. one of MIGRATION_STATUS_ACTIVE or MIGRATION_STATE_POSTCOPY_ACTIVE
(which is why it's current_*active*_state); and it's only used as the
parameter to migrate_set_state - in the same way the current code does:

                   migrate_set_state(s, MIGRATION_STATUS_ACTIVE,
                                     MIGRATION_STATUS_COMPLETED);

to ensure that any failure or cancel occuring at the same time isn't lost.

Dave
> 
> 
> > +                                              bool *old_vm_running,
> > +                                              int64_t *start_time)
> > +{
> > +    int ret;
> > +    if (s->state == MIGRATION_STATUS_ACTIVE) {
>            current_active_state = s->state;
> > +        qemu_mutex_lock_iothread();
> > +        *start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
> > +        qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
> > +        *old_vm_running = runstate_is_running();
> > +
> > +        ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
> > +        if (ret >= 0) {
> > +            qemu_file_set_rate_limit(s->file, INT64_MAX);
> > +            qemu_savevm_state_complete_precopy(s->file);
> > +        }
> > +        qemu_mutex_unlock_iothread();
> > +
> > +        if (ret < 0) {
> > +            goto fail;
> > +        }
> > +    } else if (s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
>            current_active_state = s->state;
> > +        trace_migration_thread_end_of_iteration_postcopy_end();
> > +
> > +        qemu_savevm_state_complete_postcopy(s->file);
> > +        
> > trace_migration_thread_end_of_iteration_postcopy_end_after_complete();
> > +    }
> > +
> > +    /*
> > +     * If rp was opened we must clean up the thread before
> > +     * cleaning everything else up (since if there are no failures
> > +     * it will wait for the destination to send it's status in
> > +     * a SHUT command).
> > +     * Postcopy opens rp if enabled (even if it's not avtivated)
> > +     */
> > +    if (migrate_postcopy_ram()) {
> > +        int rp_error;
> > +        trace_migration_thread_end_of_iteration_postcopy_end_before_rp();
> > +        rp_error = await_return_path_close_on_source(s);
> > +        
> > trace_migration_thread_end_of_iteration_postcopy_end_after_rp(rp_error);
> > +        if (rp_error) {
> > +            goto fail;
> > +        }
> > +    }
> > +
> > +    if (qemu_file_get_error(s->file)) {
> > +        trace_migration_thread_end_of_iteration_file_err();
> > +        goto fail;
> > +    }
> > +
> > +    migrate_set_state(s, current_active_state, MIGRATION_STATUS_COMPLETED);
> > +    return;
> > +
> > +fail:
> > +    migrate_set_state(s, current_active_state, MIGRATION_STATUS_FAILED);
> > +}
> > +
> > +/*
> >   * Master migration thread on the source VM.
> >   * It drives the migration and pumps the data down the outgoing channel.
> >   */
> > @@ -1233,31 +1294,11 @@ static void *migration_thread(void *opaque)
> >                  /* Just another iteration step */
> >                  qemu_savevm_state_iterate(s->file);
> >              } else {
> > -                int ret;
> > -
> > -                qemu_mutex_lock_iothread();
> > -                start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
> > -                qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
> > -                old_vm_running = runstate_is_running();
> > -
> > -                ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
> > -                if (ret >= 0) {
> > -                    qemu_file_set_rate_limit(s->file, INT64_MAX);
> > -                    qemu_savevm_state_complete_precopy(s->file);
> > -                }
> > -                qemu_mutex_unlock_iothread();
> > +                trace_migration_thread_low_pending(pending_size);
> >  
> > -                if (ret < 0) {
> > -                    migrate_set_state(s, MIGRATION_STATUS_ACTIVE,
> > -                                      MIGRATION_STATUS_FAILED);
> > -                    break;
> > -                }
> > -
> > -                if (!qemu_file_get_error(s->file)) {
> > -                    migrate_set_state(s, MIGRATION_STATUS_ACTIVE,
> > -                                      MIGRATION_STATUS_COMPLETED);
> > -                    break;
> > -                }
> > +                migration_thread_end_of_iteration(s, current_active_type,
> > +                    &old_vm_running, &start_time);
> > +                break;
> >              }
> >          }
> >  
> > diff --git a/trace-events b/trace-events
> > index f096877..528d5a3 100644
> > --- a/trace-events
> > +++ b/trace-events
> > @@ -1425,6 +1425,12 @@ migrate_send_rp_message(int msg_type, uint16_t len) 
> > "%d: len %d"
> >  migration_thread_after_loop(void) ""
> >  migration_thread_file_err(void) ""
> >  migration_thread_setup_complete(void) ""
> > +migration_thread_low_pending(uint64_t pending) "%" PRIu64
> > +migration_thread_end_of_iteration_file_err(void) ""
> > +migration_thread_end_of_iteration_postcopy_end(void) ""
> > +migration_thread_end_of_iteration_postcopy_end_after_complete(void) ""
> > +migration_thread_end_of_iteration_postcopy_end_before_rp(void) ""
> > +migration_thread_end_of_iteration_postcopy_end_after_rp(int rp_error) "%d"
> >  open_return_path_on_source(void) ""
> >  open_return_path_on_source_continue(void) ""
> >  postcopy_start(void) ""
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK