On 02/23/2017 08:50 AM, Michal Privoznik wrote:
On 02/23/2017 03:26 PM, Matt Fleming wrote:
On Tue, 21 Feb, at 11:23:52AM, Michal Privoznik wrote:
Jim,
what is the actual problem? I've tried to reproduce this by running vm
with 3.5G RAM backed by 1GB huge pages and the guest runs just fine. I
mean kvm guest. This is because at the cmd line level there is aligned
value:
-m size=4194304k,slots=16,maxmem=8388608k
This is result of qemuDomainAlignMemorySizes(). So perhaps there's a bug
somewhere in the function?
Quite possibly. Some memory values work fine and appear to be rounded
to the next gigabyte boundary. One KiB values that fails for me is,
<memory unit='KiB'>52428801</memory>
<currentMemory unit='KiB'>52428801</currentMemory>
Which results in qemu-kvm ... -m 51201
I currently don't have access to a host with 50+GB of RAM, so I start small:
<memory unit='KiB'>3145739</memory>
<currentMemory unit='KiB'>3145739</currentMemory>
<memoryBacking>
<hugepages>
<page size='1048576' unit='KiB'/>
</hugepages>
</memoryBacking>
-m 3073
And this works just fine. One thing that I've noticed is that we don't
take into account sizes of huge pages in qemuDomainAlignMemorySizes().
But then again - what is the scenario you're seeing? What's the error
message?
Sorry for the delay. I was having problems reproducing it until Matt reminded me
that some vNUMA was needed in the mix. E.g. config containing
<memory unit='KiB'>10000000</memory>
<currentMemory unit='KiB'>10000000</currentMemory>
<memoryBacking>
<hugepages>
<page size='1048576' unit='KiB'/>
</hugepages>
</memoryBacking>
<cpu mode='host-passthrough'>
<topology sockets='2' cores='20' threads='2'/>
<numa>
<cell id='0' cpus='0-39' memory='5000000' unit='KiB'/>
<cell id='1' cpus='40-79' memory='5000000' unit='KiB'/>
</numa>
</cpu>
fails with
2017-03-14T21:50:01.228693Z qemu-system-x86_64: -object
memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu,size=5120196608,host-nodes=0-1,policy=bind:
cannot bind memory to host NUMA nodes: Invalid argument
Changing the config by s/10000000/10485760/ and s/5000000/5242880/ works. It was
only then that I remembered the machine was running libvirt 2.0.0 :-/. I updated
to 3.1.0 and the original, unaligned config works. So there are some fixes in
the alignment code in the meanwhile. I'll test some of the other problematic
configurations, which in some cases resulted in different qemu errors, and
report back if I find any problems with current code.
Regards,
Jim
--
libvir-list mailing list
libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list
