Re: [libvirt] [Question] Collect vNode pinning to pNode run-time information
On Fri, May 16, 2014 at 03:01:14AM +0000, Shi, Xiao-Lei (Bruce, HP Servers-PSC-CQ) wrote:
Hi all,
I have a question about NUMA.
User configured vNode(guest virtual numa node), but he didn't
configure cputune and numatune. Now we want to get the information
that each vNode run in which pNode(host numa node). It's run-time
information that may be modified with high frequency.
In current Libvirt's API, we can get the information that each vCpu
running on which pCpu through virsh vcpuinfo(there should be a
corresponding Libvirt API function). But we didn't find any APIs to
get the information that each vNode uses which pNode's memory, or
just each vCpu consumes which pNode's memory.
Yes, you are correct - the libvirt APIs only provide a way to figure
out the vCPU<->pCPU placement, nothing about memory.
We find a command "numastat -mcn -p qemu" that can get the
memory
consume data of each VM, but it still loses the information that
we want(vNode memory consume data), as following:
# numastat -mcn -p qemu
Per-node process memory usage (in MBs)
PID Node 0 Node 1 Total
--------------- ------ ------ -----
8900 (qemu-kvm) 2032 50 2083
17716 (qemu-kvm) 1546 663 2209
22484 (qemu-kvm) 621 1524 2146
29694 (qemu-kvm) 892 1350 2242
--------------- ------ ------ -----
Total 5092 3588 8680
.........
My question is:
1. In Libvirt, are there any ways that we can get our
needed data?
Not at this point in time.
2. If no ways in Libvirt, do you have any other suggestions
to collect the information?
I don't believe there is any easy way. The 'numastat' command
can only see things at process-level granularity - it has no
way of knowing about the fact that the KVM process has two
virtual guest NUMA nodes.
With current QEMU there's not even any way for libvirt to
know where guest NUMA node memory is allocated from. There
is working taking place in QEMU to make it possible to
associated guest NUMA nodes with host NUMA nodes. This only
helps if the guest / host nodes are specified though.
If you are letting the guest NUMA nodes float across any
host NUMA node, I'm not sure that KVM will provide us enough
info to determine what was allocated from where. You might
want to send this query to the qemu-devel mailing list
instead to see if they have better suggestions
Regards,
Daniel
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