Re: [Qemu-devel] [PATCH v7 20/42] Modify save_live_pending for postcopy

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Juan Quintela (quintela@redhat.com) wrote:
> "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > Modify save_live_pending to return separate postcopiable and
> > non-postcopiable counts.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> 
> Reviewed-by: Juan Quintela <quintela@redhat.com>

Thanks,

> I think that if you make a small change of meaning, everything gots easier:
> 
> > -static uint64_t block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size)
> > +static void block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size,
> > +                               uint64_t *non_postcopiable_pending,
> > +                               uint64_t *postcopiable_pending)
> >  {
> >      /* Estimate pending number of bytes to send */
> >      uint64_t pending;
> > @@ -773,7 +775,8 @@ static uint64_t block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size)
> >      qemu_mutex_unlock_iothread();
> >  
> >      DPRINTF("Enter save live pending  %" PRIu64 "\n", pending);
> > -    return pending;
> > +    *non_postcopiable_pending = pending;
> > +    *postcopiable_pending = 0;
> 
> Change that two lines to:
> 
>        *non_postcopiable_pending += pending;
>        *postcopiable_pending += 0; /* ok, equivalent of doing nothing */
> 
> This way, chaining gots easier?

OK, done; I did it as:

+    /* We can do postcopy, and all the data is postcopiable */
+    *postcopiable_pending += remaining_size;

rather than having the odd += 0;

> > diff --git a/migration/savevm.c b/migration/savevm.c
> > index 2c4cbe1..ebd3d31 100644
> > --- a/migration/savevm.c
> > +++ b/migration/savevm.c
> > @@ -1012,10 +1012,20 @@ void qemu_savevm_state_complete_precopy(QEMUFile *f)
> >      qemu_fflush(f);
> >  }
> >  
> > -uint64_t qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size)
> > +/* Give an estimate of the amount left to be transferred,
> > + * the result is split into the amount for units that can and
> > + * for units that can't do postcopy.
> > + */
> > +void qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size,
> > +                               uint64_t *res_non_postcopiable,
> > +                               uint64_t *res_postcopiable)
> >  {
> >      SaveStateEntry *se;
> > -    uint64_t ret = 0;
> > +    uint64_t tmp_non_postcopiable, tmp_postcopiable;
> > +
> > +    *res_non_postcopiable = 0;
> > +    *res_postcopiable = 0;
> > +
> >  
> >      QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
> >          if (!se->ops || !se->ops->save_live_pending) {
> > @@ -1026,9 +1036,12 @@ uint64_t qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size)
> >                  continue;
> >              }
> >          }
> > -        ret += se->ops->save_live_pending(f, se->opaque, max_size);
> > +        se->ops->save_live_pending(f, se->opaque, max_size,
> > +                                   &tmp_non_postcopiable, &tmp_postcopiable);
> > +
> > +        *res_postcopiable += tmp_postcopiable;
> > +        *res_non_postcopiable += tmp_non_postcopiable;
> >      }
> > -    return ret;
> 
> With the change, we don't care in the other functions, and this one gets
> simpler IMHO.

Yep,

Dave

--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK