Re: [Qemu-devel] [PATCH 0/7] spapr: rework memory nodes

[Nishanth Aravamudan <nacc@linux.vnet.ibm.com>]

On 16.06.2014 [22:37:00 -0300], Eduardo Habkost wrote:
> On Mon, Jun 16, 2014 at 05:25:00PM -0700, Nishanth Aravamudan wrote:
> > On 16.06.2014 [17:51:50 -0300], Eduardo Habkost wrote:
> > > On Mon, Jun 16, 2014 at 06:16:29PM +1000, Alexey Kardashevskiy wrote:
> > > > On 06/16/2014 05:53 PM, Alexey Kardashevskiy wrote:
> > > > > c4177479 "spapr: make sure RMA is in first mode of first memory node"
> > > > > introduced regression which prevents from running guests with memoryless
> > > > > NUMA node#0 which may happen on real POWER8 boxes and which would make
> > > > > sense to debug in QEMU.
> > > > > 
> > > > > This patchset aim is to fix that and also fix various code problems in
> > > > > memory nodes generation.
> > > > > 
> > > > > These 2 patches could be merged (the resulting patch looks rather ugly):
> > > > > spapr: Use DT memory node rendering helper for other nodes
> > > > > spapr: Move DT memory node rendering to a helper
> > > > > 
> > > > > Please comment. Thanks!
> > > > > 
> > > > 
> > > > Sure I forgot to add an example of what I am trying to run without errors
> > > > and warnings:
> > > > 
> > > > /home/aik/qemu-system-ppc64 \
> > > > -enable-kvm \
> > > > -machine pseries \
> > > > -nographic \
> > > > -vga none \
> > > > -drive id=id0,if=none,file=virtimg/fc20_24GB.qcow2,format=qcow2 \
> > > > -device scsi-disk,id=id1,drive=id0 \
> > > > -m 2080 \
> > > > -smp 8 \
> > > > -numa node,nodeid=0,cpus=0-7,memory=0 \
> > > > -numa node,nodeid=2,cpus=0-3,mem=1040 \
> > > > -numa node,nodeid=4,cpus=4-7,mem=1040
> > > 
> > > (Note: I will ignore the "cpus" argument for the discussion below.)
> > > 
> > > I understand now that the non-contiguous node IDs are guest-visible.
> > > 
> > > But I still would like to understand the motivations for your use case,
> > > to understand which solution makes more sense.
> > > 
> > > If you really want 5 nodes, you just need to write this:
> > >   -numa node,nodeid=0,cpus=0-7,memory=0 \
> > >   -numa node,nodeid=1 \
> > >   -numa node,nodeid=2,cpus=0-3,mem=1040 \
> > >   -numa node,nodeid=3 \
> > >   -numa node,nodeid=4,cpus=4-7,mem=1040
> > > 
> > > If you just want 3 nodes, you can just write this:
> > >   -numa node,nodeid=0,cpus=0-7,memory=0 \
> > >   -numa node,nodeid=1,cpus=0-3,mem=1040 \
> > >   -numa node,nodeid=4,cpus=4-7,mem=1040
> > 
> > No, this doesn't do what you think it would :)
> 
> That was a typo. I meant:
>    -numa node,nodeid=0,cpus=0-7,memory=0 \
>    -numa node,nodeid=1,cpus=0-3,mem=1040 \
>    -numa node,nodeid=2,cpus=4-7,mem=1040

Ok, that's fair, but I think we all agree now that the goal is two-fold:

1) properly support memoryless nodes (including node 0) in ppc
2) properly support sparse NUMA numbering

Thanks,
Nish