The problem now is that because this went forth and back and sideways at
least I am now quite confused. :(
1. numa info returned by nodeinfo incorrect
-> 15.04. ok, before that incorrect for some Supermicro boards
2. numa information not automatically used
-> from my experiments and internet search this never was working and is not
working
either in upcoming 15.10 as it would require numad available in the
distro (at build
of libvirt and on the virt host).
For OpenStack nova [1] there was some work done for their Juno series.
That possibly did not get into 14.04 but also sounds independent to what
standalone libvirt would or could do.
3. Manual tuning for numa appears to be possible and working even in 14.04. But
since my
nodeinfo is ok, I cannot say whether that really affects numa tuning. Some
comments in
the code sound like the info that matters would be the capabilities one.
Which according
to some comments here is ok even if nodeinfo is not.
So for memory, would numatune on a running but not tuned guest return a
range covering the correct available set of nodes? Which then can be
tuned (with --config) to be limited to a defined node. That only works
the next time the related qemu task is started (so probably needs a
shutdown + start). Can be verified with numastat.
For the VCPUs a cpuset can be added to the vcpu xml element.
Unfortunately there does not seem to be a command doing so. Which is
inconvenient. One could use vcpupin but that needs to be done for each
vcpu individually. With vcpuinfo this can be verified.
So if manual memory or cpu pinning is broken in a supported release,
this would be important to fix (though should get a different bug report
to keep confusion low). For the nodeinfo part it depends on whether this
has influence on the actual tuning. If it has not it still would be good
to resolve it but less urgent.
I suspect the memory pinning is the part that is more likely the problem
as vcpu pinning does not really care about nodes for its function. And
the way memory pinning is done only looks to work when the qemu process
gets started within a contrainted memory cgroup. So modifying a running
guest would have no effect but that consistently on all releases as that
seems to depend on numad.
[1] https://blueprints.launchpad.net/nova/+spec/virt-driver-numa-
placement
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https://bugs.launchpad.net/bugs/1446177
Title:
Nodeinfo returns wrong NUMA topology / bad virtualization performance
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