[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [libvirt] [RFC PATCH v1 0/4] Add cpu hotplug support to libvirt.



On 09/03/2012 08:06 AM, Tang Chen wrote:
It seems that libvirt is not cpu hotplug aware.
Please refer to the following problem.

1. At first, we have 2 cpus.
# cat /cgroup/cpuset/cpuset.cpus
0-1
# cat /cgroup/cpuset/libvirt/qemu/cpuset.cpus
0-1

2. And we have a vm1 with following configuration.
   <cputune>
     <vcpupin vcpu='0' cpuset='1'/>
     <hypervisorpin cpuset='1'/>
   </cputune>

3. Offline cpu1.
# echo 0 > /sys/devices/system/cpu/cpu1/online
# cat /sys/devices/system/cpu/cpu1/online
0
# cat /cgroup/cpuset/cpuset.cpus
0
# cat /cgroup/cpuset/libvirt/qemu/cpuset.cpus
0
# cat /cgroup/cpuset/libvirt/lxc/cpuset.cpus
0

4. Online cpu1.
# echo 1 > /sys/devices/system/cpu/cpu1/online
# cat /sys/devices/system/cpu/cpu1/online
1
# cat /cgroup/cpuset/cpuset.cpus
0-1
# cat /cgroup/cpuset/libvirt/cpuset.cpus
0
# cat /cgroup/cpuset/libvirt/qemu/cpuset.cpus
0
# cat /cgroup/cpuset/libvirt/lxc/cpuset.cpus
0

Here,cgroup updated cpuset.cpus,but not for libvirt directory,and also qemu and lxc directory.
vm1 cannot be started again.
# virsh start vm1
error: Failed to start domain vm1
error: Unable to set cpuset.cpus: Permission denied

And libvird gave the following errors.
2012-07-17 07:30:22.478+0000: 3118: error : qemuSetupCgroupVcpuPin:498 : Unable to set cpuset.cpus: Permission denied


These patches resolves this problem by listening on the netlink for cpu hotplug event.
When the netlink service gets the cpu hotplug event, it will attract the cpuid in the message,
and add it into cpuset.cpus in:
     /cgroup/cpuset/libvirt
     /cgroup/cpuset/libvirt/qemu
     /cgroup/cpuset/libvirt/lxc


Hi,

this approach requires that libvirtd keeps running through the entire lifecycle of a guest. That is something that cannot be safely assumed and therefore hotplug events can be missed. That means that libvirt must synchronize the hypervisors cpusets with the host's current CPU states. You could do that for instance when registering the callback.

--

Mit freundlichen Grüßen/Kind Regards
   Viktor Mihajlovski

IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Martin Jetter
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]