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numa: forbid '-numa node, mem' for 5.1 and newer machine types

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Deprecation period is run out and it's a time to flip the switch
introduced by cd5ff8333a.  Disable legacy option for new machine
types (since 5.1) and amend documentation.

'-numa node,memdev' shall be used instead of disabled option
with new machine types.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <20200609135635.761587-1-imammedo@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Igor Mammedov 2020-06-09 09:56:35 -04:00 • committed by Paolo Bonzini
parent f9919116b8
commit 32a354dc6c
8 changed files with 36 additions and 24 deletions
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37
docs/system/deprecated.rst
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@ -95,23 +95,6 @@ error in the future.
The ``-realtime mlock=on|off`` argument has been replaced by the
``-overcommit mem-lock=on|off`` argument.
``-numa node,mem=``\ *size* (since 4.1)
'''''''''''''''''''''''''''''''''''''''
The parameter ``mem`` of ``-numa node`` is used to assign a part of
guest RAM to a NUMA node. But when using it, it's impossible to manage specified
RAM chunk on the host side (like bind it to a host node, setting bind policy, ...),
so guest end-ups with the fake NUMA configuration with suboptiomal performance.
However since 2014 there is an alternative way to assign RAM to a NUMA node
using parameter ``memdev``, which does the same as ``mem`` and adds
means to actualy manage node RAM on the host side. Use parameter ``memdev``
with *memory-backend-ram* backend as an replacement for parameter ``mem``
to achieve the same fake NUMA effect or a properly configured
*memory-backend-file* backend to actually benefit from NUMA configuration.
In future new machine versions will not accept the option but it will still
work with old machine types. User can check QAPI schema to see if the legacy
option is supported by looking at MachineInfo::numa-mem-supported property.
``-numa`` node (without memory specified) (since 4.1)
'''''''''''''''''''''''''''''''''''''''''''''''''''''
@ -553,3 +536,23 @@ long starting at 1MiB, the old command::
can be rewritten as::
qemu-nbd -t --image-opts driver=raw,offset=1M,size=100M,file.driver=qcow2,file.file.driver=file,file.file.filename=file.qcow2
Command line options
--------------------
``-numa node,mem=``\ *size* (removed in 5.1)
''''''''''''''''''''''''''''''''''''''''''''
The parameter ``mem`` of ``-numa node`` was used to assign a part of
guest RAM to a NUMA node. But when using it, it's impossible to manage a specified
RAM chunk on the host side (like bind it to a host node, setting bind policy, ...),
so the guest ends up with the fake NUMA configuration with suboptiomal performance.
However since 2014 there is an alternative way to assign RAM to a NUMA node
using parameter ``memdev``, which does the same as ``mem`` and adds
means to actually manage node RAM on the host side. Use parameter ``memdev``
with *memory-backend-ram* backend as replacement for parameter ``mem``
to achieve the same fake NUMA effect or a properly configured
*memory-backend-file* backend to actually benefit from NUMA configuration.
New machine versions (since 5.1) will not accept the option but it will still
work with old machine types. User can check the QAPI schema to see if the legacy
option is supported by looking at MachineInfo::numa-mem-supported property.