On 19.05.2014 [15:37:52 -0700], Nishanth Aravamudan wrote: > Hi Alexey, > > I've been looking at hw/ppc/spapr.c::spapr_populate_memory() and ran > into a few questions: > > 1) The values from 1 to nb_numa_nodes are used as indices into the > node_mem array, but that is not populated, necessarily, linearly. > vl.c::add_node() uses the nodeid parameter as the index into node_mem, > if it is specified. > > 2) The node ID is based upon the index into the array, but it seems like > it should actually be based upon the nodeid specified, if any. That is, > we set the value at index 4 (which is statically the reference point in > 'ibm,associativity-reference-points') of 'ibm,associativty' for each > 'ibm,memory@....' node to the index we are currently at. But as > mentioned in 1) above that index isn't necessarily currently the nodeid > specified on the command-line. > > What this all means, is that if I specify something like: > > -numa node,nodeid=1,cpus=0-7,mem=2048 -numa > node,nodeid=5,cpus=8-15,mem=0 -numa node,nodeid=9,mem=2048 > > Linux sees: > > numactl --hardware > available: 3 nodes (0-2) > node 0 cpus: 8 9 10 11 12 13 14 15 > node 0 size: 0 MB > node 0 free: 0 MB > node 1 cpus: 0 1 2 3 4 5 6 7 > node 1 size: 2024 MB > node 1 free: 1560 MB > node 2 cpus: > node 2 size: 0 MB > node 2 free: 0 MB > > Maybe we don't really care about this, but I just noticed it when trying > to reproduce some really weird topologies from PowerVM.
Upon further investigation into node_mem, it seems like this assumption is present throughout the qemu code, e.g, the qemu monitor 'info numa' command. Will just document it for myself as a weird way to make memoryless nodes show up :) Thanks, Nish
