On Fri, Mar 03, 2017 at 10:09:22AM -0600, Eric Blake wrote: > On 03/03/2017 07:57 AM, Eduardo Habkost wrote: > > >> With this patch, when a user wants to create a guest that contains > >> several vNUMA nodes and also wants to set distance among those nodes, > >> the QEMU command would like: > >> > >> ``` > >> -object > >> memory-backend-ram,size=1G,prealloc=yes,host-nodes=0,policy=bind,id=node0 \ > >> -numa > >> node,nodeid=0,cpus=0,memdev=node0,distance=10,distance=21,distance=31,distance=41 > >> \ > > > > > It would be nice to have a more intuitive syntax to represent > > ordered lists in QemuOpts. But this is what we have today. > > > > Markus has the discussion on representing arrays via the command line; > particularly since this array is very tightly coupled to the order in > which values are presented, it may be worth having: > > -numa > node,nodeid=0,cpus=0,memdev=nod0,distance.0=10,distance.1=21,distance.2=31,distance.3=41 > > with the explicit distance.0= suffixes to distance making it more > obvious that we are dealing with an array. > > > I think the proposal makes sense. I would like the semantics of the new > > option > > to be documented at qapi-schema.json and qemu-options.hx. > > > > I would call the new NumaNodeOptions field "distances", as it is > > a list of distances. > > Indeed, Markus is trying (with his work on -blockdev for 2.9) to get the > command line to a point where it is identical to the QMP code, by > reusing qapi-schema.json, so we should very much keep that in mind with > whatever we add to -numa in 2.10. > > > > but in the future we could support something like: > > > > -numa node,nodeid=0,cpus=0,memdev=node0 \ > > -numa node,nodeid=1,cpus=1,memdev=node1 \ > > -numa node,nodeid=2,cpus=2,memdev=node2 \ > > -numa node,nodeid=3,cpus=3,memdev=node3 \ > > -numa > > distances,distances[0][0]=10,distances[0][1]=21,distances[0][2]=31,distances[0][3]=41,\ > > > > distances[1][0]=21,distances[1][1]=10,distances[1][2]=21,distances[1][3]=31,\ > > > > distances[2][0]=31,distances[2][1]=21,distances[2][2]=10,distances[2][3]=21,\ > > > > distances[3][0]=41,distances[3][1]=31,distances[3][2]=21,distances[3][3]=10 > > Except that [] requires special shell quoting, so the proposal would be > more like: > > -numa distances.0.0=10,distances.0.1=21 > > Right now, QMP doesn't support 2-D arrays (although this may be a good > reason to introduce support), so that's also something to think about > (not insurmountable, but makes the task more complex).
What I don't like about this syntax is that it is duplicating information twice. IIUC the NUMA distance information is unidirectional, so specifying the same data for both direetions (node 0 -> node 3, and node 3 -> node 0) looks like overkill. Also the self-node distance isi defined to always be 10 IIUC, so specifying that is not required. IOW, could cut down the data we need to provider to just -numa distances,nodea=0,nodeb=1,value=20 -numa distances,nodea=0,nodeb=2,value=20 -numa distances,nodea=0,nodeb=3,value=20 -numa distances,nodea=1,nodeb=2,value=20 -numa distances,nodea=1,nodeb=3,value=20 -numa distances,nodea=2,nodeb=3,value=20 Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :|
