Re: [Qemu-devel] [PATCH v4 0/3] numa: deprecate '-numa node, mem' and default memory distribution

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 30 May 2019 10:33:16 +0200
Igor Mammedov <imammedo@redhat.com> wrote:

> Changes since v3:
>   - simplify series by dropping idea of showing property values in "qom-list-properties"
>     and use MachineInfo in QAPI schema instead
> 
> Changes since v2:
>   - taking in account previous review, implement a way for mgmt to intospect if
>     '-numa node,mem' is supported by machine type as suggested by Daniel at
>              https://www.mail-archive.com/qemu-devel@nongnu.org/msg601220.html
>       * ammend "qom-list-properties" to show property values
>       * add "numa-mem-supported" machine property to reflect if '-numa node,mem=SZ'
>         is supported. It culd be used with '-machine none' or at runtime with
>         --preconfig before numa memory mapping are configured
>   * minor fixes to deprecation documentation mentioning "numa-mem-supported" property
> 
>  1) "I'm considering to deprecating -mem-path/prealloc CLI options and replacing
> them with a single memdev Machine property to allow interested users to pick
> used backend for initial RAM (fixes mixed -mem-path+hostmem backends issues)
> and as a transition step to modeling initial RAM as a Device instead of
> (ab)using MemoryRegion APIs."
> (for more details see: https://www.mail-archive.com/qemu-devel@nongnu.org/msg596314.html)
> 
> However there is a couple of roadblocks on the way (s390x and numa memory handling).
> I think I finally thought out a way to hack s390x in migration compatible manner,
> but I don't see any way to do it for -numa node,mem and default RAM assignement
> to nodes. Considering both numa usecases aren't meaningfully using NUMA (aside
> guest side testing) and could be replaced with explicitly used memdev parameter,
> I'd like to propose removing these fake NUMA friends on new machine types,
> hence this deprecation. And once the last machie type that supported the option
> is removed we would be able to remove option altogether.
> 
> As result of removing deprecated options and replacing initial RAM allocation
> with 'memdev's (1), QEMU will allocate guest RAM in consistent way, fixing mixed
> use-case and allowing boards to move towards modelling initial RAM as Device(s).
> Which in its own turn should allow to cleanup NUMA/HMP/memory accounting code
> more by dropping ad-hoc node_mem tracking and reusing memory device enumeration
> instead.

Eduardo,

could you take and merge it via numa/machine tree?

> 
> Reference to previous versions:
>  * https://www.mail-archive.com/qemu-devel@nongnu.org/msg617694.html
> 
> CC: libvir-list@redhat.com
> CC: ehabkost@redhat.com
> CC: pbonzini@redhat.com
> CC: berrange@redhat.com
> CC: armbru@redhat.com
> 
> Igor Mammedov (3):
>   machine: show if CLI option '-numa node,mem' is supported in QAPI
>     schema
>   numa: deprecate 'mem' parameter of '-numa node' option
>   numa: deprecate implict memory distribution between nodes
> 
>  include/hw/boards.h  |  3 +++
>  hw/arm/virt.c        |  1 +
>  hw/i386/pc.c         |  1 +
>  hw/ppc/spapr.c       |  1 +
>  numa.c               |  5 +++++
>  qapi/misc.json       |  5 ++++-
>  qemu-deprecated.texi | 24 ++++++++++++++++++++++++
>  vl.c                 |  1 +
>  8 files changed, 40 insertions(+), 1 deletion(-)
>