[libvirt] [PATCH v2 0/2] qemu: Honor memory mode='strict'

[Michal Privoznik]

On 4/11/19 4:23 PM, Daniel Henrique Barboza wrote:
> Hi,
> 
> I've tested these patches again, twice, in similar setups like I tested
> the first version (first in a Power8, then in a Power9 server).
> 
> Same results, though. Libvirt will not avoid the launch of a pseries guest,
> with numanode=strict, even if the numa node does not have available
> RAM. If I stress test the memory of the guest to force the allocation,
> QEMU exits with an error as soon as the memory of the host numa node
> is exhausted.

Yes, this is expected. I mean, by default qemu doesn't allocate memory 
for the guest fully. You'd have to force it:

<memoryBacking>
   <allocation mode='immediate'/>
</memoryBacking>

> 
> If I change the numanode setting to 'preferred' and repeats the test, QEMU
> doesn't exit with an error - the process starts to take memory from other
> numa nodes. This indicates that the numanode policy is apparently being
> forced in the QEMU process - however, it is not forced in VM boot.
> 
> I've debugged it a little and haven't found anything wrong that jumps the
> eye. All functions that succeeds qemuSetupCpusetMems exits out with
> ret = 0. Unfortunately, I don't have access to a x86 server with more than
> one NUMA node to compare results.
> 
> Since I can't say for sure if what I'm seeing is an exclusive pseries
> behavior, I see no problem into pushing this series upstream
> if it makes sense for x86. We can debug/fix the Power side later.

I bet that if you force the allocation then the domain will be unable to 
boot.

Thanks for the testing!

Michal