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Description of problem:
set emulator_period failed, return "error: Unable to find emulator cgroup for rhel7: No such file or directory"

Version-Release number of selected component (if applicable):
libvirt-1.0.5-1.el7.x86_64
qemu-kvm-1.4.0-4.el7.x86_64
kernel-3.9.0-0.55.el7.x86_64

How reproducible:
100%

Steps:

1. edit a domain with:
  <vcpu placement='auto'>2</vcpu>
  <cputune>
    <shares>2048</shares>
    <period>1000000</period>
    <quota>1000</quota>
    <emulator_period>1000000</emulator_period>
    <emulator_quota>1000</emulator_quota>
    <vcpupin vcpu='0' cpuset='0'/>
    <vcpupin vcpu='1' cpuset='1'/>
    <emulatorpin cpuset='2'/>
  </cputune>


2. start it
[root@dhcp-66-71-41 ~]# virsh start rhel7

3. check schedinfo 
[root@dhcp-66-71-41 ~]# virsh schedinfo rhel7
Scheduler      : posix
cpu_shares     : 2048
vcpu_period    : 1000000
vcpu_quota     : 1000
emulator_period: 1000000
emulator_quota : 1000

4. set emulator_period
[root@dhcp-66-71-41 ~]# virsh schedinfo rhel7 --set emulator_period=900000
Scheduler      : posix
error: Unable to find emulator cgroup for rhel7: No such file or directory

Actual results:
cannot set emulator_period. 

Expected results:
set emulator_period successfully.

this bug is still in libvirt-1.0.5-2.el7.x86_64.

I've found out the problem, but not the root cause, yet.  I'm bisecting the sources now, so I'm assigning it to myself.

Moving to POST with upstream commit v1.0.5-243-g0471637:

commit 0471637d5628106d058f0eb5516ffa7d5285cc6f
Author: Martin Kletzander <mkletzan>
Date:   Thu May 16 14:37:54 2013 +0200

    qemu: Fix cgroup handling when setting VCPU BW

This bug fix is verified.

# rpm -q libvirt
libvirt-1.0.6-1.el7.x86_64

# virsh schedinfo rhel7
Scheduler      : posix
cpu_shares     : 2048
vcpu_period    : 1000000
vcpu_quota     : 1000
emulator_period: 1000000
emulator_quota : 1000

# virsh schedinfo rhel7 --set emulator_period=900000
Scheduler      : posix
cpu_shares     : 2048
vcpu_period    : 1000000
vcpu_quota     : 1000
emulator_period: 900000
emulator_quota : 1000

This request was resolved in Red Hat Enterprise Linux 7.0.

Contact your manager or support representative in case you have further questions about the request.