Re: [libvirt] 1GB huge pages and incompatible VM memory size
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?
Michal