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Re: [libvirt] memory pinning problem



On Tue, Aug 27, 2013 at 09:09:25AM +0200, David Weber wrote:
> Hi,
> 
> we try to use vcpu pinning on a 2 socket server with Intel Xeon E5620 cpus, HT 
> enabled and 2*6*16GiB Ram but experience problems if we try to start a guest 
> on the second socket:
> error: Failed to start domain test
> error: internal error: process exited while connecting to monitor: 
> kvm_init_vcpu failed: Cannot allocate memory
> 
> Libvirt version 1.1.1 
> Linux 3.11-rc7
> 
> Because I coudn't find any other service which allowed a 7M file upload, I put 
> the log file and everything else which could perhabs be relevant into a github 
> repository:
> https://github.com/David-Weber/vcpu-pinning
> 
> When we try to start a guest on the first node it runs fine:
>   <vcpu placement='static' cpuset='0-3,8-11'>4</vcpu>
>   <numatune>
>     <memory mode='strict' nodeset='0'/>
>   </numatune>
> 
> Starting it on the second node fails
>   <vcpu placement='static' cpuset='4-7,12-15'>4</vcpu>
>   <numatune>
>     <memory mode='strict' nodeset='1'/>
>   </numatune>
> 
> Even more strange, starting it with the CPUs of the second node and the memory 
> of the first node works:
>   <vcpu placement='static' cpuset='4-7,12-15'>4</vcpu>
>   <numatune>
>     <memory mode='strict' nodeset='0'/>
>   </numatune>
> 
> The log file contains these three cases.
> 
> Using the placement='auto' parameter leads to the same problem. If numad 
> return the second node, the guest won't start.
> 
> Is this a configuration, a libvirt or a cgroup problem? :)

With mode='strict' you are telling QEMU that if it can't allocate
memory from the requested node, it should fail. Is it possible
that some of your Numa nodes have insufficient memory free ?

The combination of 'virsh capabilities' output and the results
of 'virsh freecell NODENUM' for each NUMA node will give an
indication of the allocation state.


Daniel
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