[libvirt] with vhostuser I cannot use hugepages

[Mooney, Sean K]

Ah I see the error

You have
<memoryBacking>
    <hugepages/>
      <page size='1' unit='G' nodeset='0'/>
  </memoryBacking>


Not
<memoryBacking>
    <hugepages>
      <page size='1' unit='G' nodeset='0'/>
    </hugepages>
  </memoryBacking>


From: Adnan Mundres [mailto:amundres at yahoo.com]
Sent: Wednesday, January 24, 2018 9:05 PM
To: Mooney, Sean K <sean.k.mooney at intel.com>; libvir-list at redhat.com
Subject: Re: [libvirt] with vhostuser I cannot use hugepages

Hi Sean
,

Thanks for you reply. I do have hugepages configuration in my xml and still it is not getting the memory from Hugepage. Following is my complete xml file

<domain type='kvm'>
  <uuid>c1f7a3d0-ccb7-4a85-b0f0-dd4bab73ba54</uuid>
  <description>Timos VM</description>
  <memory>16777216</memory>
  <currentMemory>16777216</currentMemory>
  <cpu mode='host-model'>
    <numa>
      <cell id="0" cpus="0" memory="16777216" unit='KiB' memAccess="shared"/>
    </numa>
   </cpu>
  <memoryBacking>
    <hugepages/>
      <page size='1' unit='G' nodeset='0'/>
  </memoryBacking>
  <numatune>
    <memory mode='strict' nodeset='1'/>
  </numatune>
  <vcpu current='7'>7</vcpu>
  <cputune>
    <vcpupin vcpu='0' cpuset='2'/>
    <vcpupin vcpu='1' cpuset='3'/>
    <vcpupin vcpu='2' cpuset='4'/>
    <vcpupin vcpu='3' cpuset='5'/>
    <vcpupin vcpu='4' cpuset='6'/>
    <vcpupin vcpu='5' cpuset='7'/>
    <vcpupin vcpu='6' cpuset='8'/>
    <emulatorpin cpuset="0,1"/>
  </cputune>
  <os>
    <type arch='x86_64' machine='pc'>hvm</type>
    <smbios mode='sysinfo'/>
  </os>
  <sysinfo type ='smbios'
  <clock offset='utc'>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='rtc' tickpolicy='delay'/>
  </clock>
  <devices>
    <emulator>/usr/libexec/qemu-kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='none'/>
      <source file='/mvmgptb11/images/flexibed/vm_5/sros-vm.qcow2'/>
      <target dev='hda' bus='virtio'/>
    </disk>
    <interface type='bridge'>
      <mac address='FA:AC:A5:00:7E:00'/>
      <source bridge='breth0'/>
      <model type='virtio'/>
    </interface>
    <interface type='bridge'>
      <mac address='FA:AC:A5:00:7E:01'/>
      <source bridge='breth1'/>
      <model type='virtio'/>
    </interface>
    <interface type='vhostuser'>
      <mac address='FA:AC:A5:00:7E:02'/>
      <source type='unix' path='/var/run/openvswitch/vhost-user-1' mode='client'/>
      <model type='virtio'/>
    </interface>
    <interface type='vhostuser'>
      <mac address='FA:AC:A5:00:7E:04'/>
      <source type='unix' path='/var/run/openvswitch/vhost-user-3' mode='client'/>
      <model type='virtio'/>
    </interface>
    <interface type='vhostuser'>
      <mac address='FA:AC:A5:00:7E:05'/>
      <source type='unix' path='/var/run/openvswitch/vhost-user-2' mode='client'/>
      <model type='virtio'/>
    </interface>
    <console type='tcp'>
      <source mode='bind' host='0.0.0.0' service='2501'/>
      <protocol type='telnet'/>
      <target type='virtio' port='0'/>
    </console>
    <watchdog model='i6300esb' action='reset'/>
  </devices>
  <seclabel type='none'/>
</domain>


On Wednesday, January 24, 2018 12:54 PM, "Mooney, Sean K" <sean.k.mooney at intel.com<mailto:sean.k.mooney at intel.com>> wrote:



From: Mooney, Sean K
Sent: Wednesday, January 24, 2018 8:52 PM
To: Adnan Mundres <amundres at yahoo.com<mailto:amundres at yahoo.com>>; libvir-list at redhat.com<mailto:libvir-list at redhat.com>
Cc: Mooney, Sean K <sean.k.mooney at intel.com<mailto:sean.k.mooney at intel.com>>
Subject: RE: [libvirt] with vhostuser I cannot use hugepages



From: libvir-list-bounces at redhat.com<mailto:libvir-list-bounces at redhat.com> [mailto:libvir-list-bounces at redhat.com] On Behalf Of Adnan Mundres
Sent: Wednesday, January 24, 2018 6:54 PM
To: libvir-list at redhat.com<mailto:libvir-list at redhat.com>
Subject: [libvirt] with vhostuser I cannot use hugepages

In my setup I am using qemu-kvm without openstack. I am trying to use ovs with dpdk. In my xml file I added following lines for the dpdkvhostuser

<cpu mode='host-passthrough'>
    <numa>
      <cell id="0" cpus="0-6" memory="16777216" unit='KiB' memAccess="shared"/>
    </numa>
 </cpu>
[Mooney, Sean K] this xml snippit is not requsting the use of huge page memory.
It is requesting memory to be allocated form a single numa node  and for that to be mmaped shared.
Dpdk does not actually need the guest to use hugepages it just improves the performance. What it requires
Is that the gues uses file descriptor backed, pre allocated, locked, shared memory.
e.g.
  <memoryBacking>
    <locked/>
    <source type='file'/>
    <access mode='shared'/>
    <allocation mode='immediate'/>
  </memoryBacking>

Hugepages will enable all of the above features implicitly.

to enable hugepages  add

<memoryBacking>
<hugepages>
      <page size="16" unit="G" nodeset="0"/>
    </hugepages>
</memoryBacking>

[Mooney, Sean K]  oh I forgot to say you can find the relevant documentation here https://libvirt.org/formatdomain.html#elementsMemoryBacking

I have enabled hugepages during boot time

ot at mvmgptb11hyp01 hyp-1]# cat /proc/meminfo | grep -i huge
AnonHugePages: 126976 kB
HugePages_Total: 100
HugePages_Free: 80
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 1048576 kB

But When I start my vm (virsh start vm1.xml) I am seeing that this vm is not using memory from hugepages, rather it is taking memory from total memory. When I checked the log file I see that it is using

-object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/var/lib/libvirt/qemu/ram,share=yes

It should use backend memory as following

-object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/vm1,share=yes

Any idea how can I use memory from hugepages

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