On 4/11/19 7:29 PM, Daniel Henrique Barboza wrote:
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.
Ah, so looks like -mem-prealloc doesn't work at Power? Can you please check:
1) that -mem-prealloc is on the qemu command line
2) how much memory qemu allocates right after it started the guest? I
mean, before you start some mem stress test which causes it to allocate
the memory fully.
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.
Yeah, I don't know Power well enough to help you. Sorry.
Michal
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