On 22.04.2014 [19:27:51 +1000], Benjamin Herrenschmidt wrote:
> On Tue, 2014-04-22 at 19:12 +1000, Alexey Kardashevskiy wrote:
> > I already have in plan to fix non-power-of-two sized memory nodes so I will
> > this too.
> >
> > What exactly is the point in having NUMA memoryless nodes now? We do
> > not support memory hotplug yet and balloon is not memory hotplug at
> > all.
>
> It exists on real HW an it's always causing funny bugs, so being able to
> simulate it in qemu would make it easier to test & debug.
Yes, my primary purpose here is to help test & debug issues I see in
other environments.
> > And I still fail to see how the patch is wrong. May be the idea of
> > having DT memory nodes the same thing as NUMA memory nodes is not
> > the best one, but the patch is not changing that.
No, but it does make it an error for the RMA not be in node0.
+ if (spapr->rma_size > node0_size) {
+ fprintf(stderr, "Error: Numa node 0 has to span the RMA (%#08"HWADDR_PR
+ spapr->rma_size);
+ exit(1);
+ }
which will never be the case if node0 has no memory?
I'm fine with the change being left in, I guess, I just want to make
sure the semantics are intended.
FWIW, if one instead tries to specify node 1 as memoryless, and nodes 0
and 2 as having memory:
sprintf(mem_name, "memory@" TARGET_FMT_lx, mem_start);
off = fdt_add_subnode(fdt, 0, mem_name);
_FDT(off);
ends up getting a duplicate error from _FDT because we're trying
to create memory@<end of node 0> twice, once for node 1 and once for
node 2. I'm not actually sure what we're supposed to do in that
situation. Looking at a PowerVM LPAR with the following topology [1]:
numactl --hardware
available: 3 nodes (1-3)
node 1 cpus: 0 1 2 3 4 5 6 7 8 9 10 11
node 1 size: 0 MB
node 1 free: 0 MB
node 2 cpus:
node 2 size: 7935 MB
node 2 free: 7302 MB
node 3 cpus:
node 3 size: 8396 MB
node 3 free: 8338 MB
node distances:
node 1 2 3
1: 10 20 20
2: 20 10 20
3: 20 20 10
I only see /proc/device-tree/memory@0. Perhaps the node 2 and node 3 are
from ibm,dynamic-reconfiguration-memory?
Thanks,
Nish
[1] Running a hacked kernel that doesn't require node 0 to be present in
the first place.
