Re: [libvirt] [Qemu-devel] [PATCH 1/2] numa: deprecate 'mem' parameter of '-numa node' option

On Fri, 1 Mar 2019 15:49:47 +0000 Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > On Fri, Mar 01, 2019 at 04:42:15PM +0100, Igor Mammedov wrote: > > The parameter allows to configure fake NUMA topology where guest > > VM simulates NUMA topology but not actually getting a performance > > benefits from it. The same or better results could be achieved > > using 'memdev' parameter. In light of that any VM that uses NUMA > > to get its benefits should use 'memdev' and to allow transition > > initial RAM to device based model, deprecate 'mem' parameter as > > its ad-hoc partitioning of initial RAM MemoryRegion can't be > > translated to memdev based backend transparently to users and in > > compatible manner (migration wise). > > > > That will also allow to clean up a bit our numa code, leaving only > > 'memdev' impl. in place and several boards that use node_mem > > to generate FDT/ACPI description from it. > > Can you confirm that the 'mem' and 'memdev' parameters to -numa > are 100% live migration compatible in both directions ? Libvirt > would need this to be the case in order to use the 'memdev' syntax > instead. Unfortunately they are not migration compatible in any direction, if it where possible to translate them to each other I'd alias 'mem' to 'memdev' without deprecation. The former sends over only one MemoryRegion to target, while the later sends over several (one per memdev).