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

On 4/11/19 11:56 AM, Michal Privoznik wrote: > 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> > Tried with this extra setting, still no good. Domain still boots, even if there is not enough memory to load up all its ram in the NUMA node I am setting. For reference, this is the top of the guest XML:   <name>vm1</name>   <uuid>f48e9e35-8406-4784-875f-5185cb4d47d7</uuid>   <memory unit='KiB'>314572800</memory>   <currentMemory unit='KiB'>314572800</currentMemory>   <memoryBacking>     <allocation mode='immediate'/>   </memoryBacking>   <vcpu placement='static'>16</vcpu>   <numatune>     <memory mode='strict' nodeset='0'/>   </numatune>   <os>     <type arch='ppc64' machine='pseries'>hvm</type>     <boot dev='hd'/>   </os>   <clock offset='utc'/> While doing this test, I recalled that some of my IBM peers recently mentioned that they were unable to do a pre-allocation of the RAM of a pseries guest using Libvirt, but they were able to do it using QEMU directly (using -realtime mlock=on). In fact, I just tried it out with command line QEMU and the guest allocated all the memory at boot.

This means that the pseries guest is able to do mem pre-alloc. I'd say that there might be something missing somewhere (XML, host setup, libvirt config ...) or perhaps even a bug that is preventing Libvirt from doing this pre-alloc. This explains why I can't verify this patch series. I'll see if I dig it further to understand why when I have the time.