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Re: [Qemu-devel] [PATCH V13 10/13] NUMA: add qmp command set-mem-policy
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH V13 10/13] NUMA: add qmp command set-mem-policy to set memory policy for NUMA node |
Date: |
Fri, 04 Oct 2013 10:13:31 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130923 Thunderbird/17.0.9 |
Il 04/10/2013 02:04, Marcelo Tosatti ha scritto:
>>> > > This QMP command allows user set guest node's memory policy
>>> > > through the QMP protocol. The qmp-shell command is like:
>>> > > set-mem-policy nodeid=0 policy=membind relative=true host-nodes=0-1
>>> > >
>>> > > Reviewed-by: Luiz Capitulino <address@hidden>
>>> > > Signed-off-by: Wanlong Gao <address@hidden>
>> >
>> > Wanlong Gao,
>> >
>> > 1)
>> >
>> > Exposing mbind via QMP/HMP on a live guest is interesting because,
>> > see mbind manpage:
>> >
>> > "By default, mbind() only has an effect for new allocations;
>> > if the pages inside the range have been already touched before
>> > setting the policy, then the policy has no effect. This default
>> > behavior may be overridden by the MPOL_MF_MOVE and
>> > MPOL_MF_MOVE_ALL flags described below."
>> >
>> > This means that executing set-mem-policy on a live guest is
>> > unpredictable: it depends on which pages have been faulted in already.
>> >
>> > Should the command be restricted to offline guests?
> In fact, unless there is a missing point, it should be removed: to solve
> the device assignment case (memory pinning), mbind must be executed before
> the memory regions are registered.
>
Right. We can add the command back later as memory-add, together with
memory hotplug.
Paolo