Re: [Qemu-devel] [PATCH v5 05/17] migration: Create x-multifd-threads parameter

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

* Juan Quintela (quintela@redhat.com) wrote:
> "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> > * Juan Quintela (quintela@redhat.com) wrote:
> >> Indicates the number of threads that we would create.  By default we
> >> create 2 threads.
> >> 
> >> Signed-off-by: Juan Quintela <quintela@redhat.com>
> >> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> >
> > Also needs updating DEFINE_PROP stuff - and if Markus' qapi patch lands.
> 
> Done.
> 
> >>  #
> >>  # @return-path: If enabled, migration will use the return path even
> >>  #               for precopy. (since 2.10)
> >> +#
> >>  # @x-multifd: Use more than one fd for migration (since 2.10)
> >>  #
> >>  # Since: 1.2
> >> @@ -910,6 +911,7 @@
> >>    'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',
> >>             'compress', 'events', 'postcopy-ram', 'x-colo', 'release-ram',
> >>             'block', 'return-path', 'x-multifd'] }
> >> +
> >
> > Escapee from previous patch.
> 
> Done.
> 
> >
> >>  ##
> >>  # @MigrationCapabilityStatus:
> >>  #
> >> @@ -1026,13 +1028,19 @@
> >>  # 	migrated and the destination must already have access to the
> >>  # 	same backing chain as was used on the source.  (since 2.10)
> >>  #
> >> +# @x-multifd-threads: Number of threads used to migrate data in
> >> +#                     parallel. This is the same number that the
> >> +#                     number of sockets used for migration.
> >> +#                     The default value is 2 (since 2.10)
> >> +#
> >
> > That did make me think for a moment; I guess '2' makes sense once you've
> > set the x-multifd capability on.  The other possibility would be to
> > remove the capability and just rely on the threads > 1
> 
> I think this is the same that xbzrle cache size.  It has a default
> value.  But we only used it when we set the capability.
> 
> I think that it makes the code more ortogonal with the others, no?

I don't have a strong view either way; it's more orthogonal vs one less
parameter.  Your choice.

Dave

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