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Bug 850718 - RFE: Reduce the depth of libvirt cgroup hierarchy
Summary: RFE: Reduce the depth of libvirt cgroup hierarchy
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: libvirt
Version: 7.0
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Daniel Berrangé
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks: 797489
TreeView+ depends on / blocked
 
Reported: 2012-08-22 08:42 UTC by Daniel Berrangé
Modified: 2014-06-18 00:41 UTC (History)
8 users (show)

Fixed In Version: libvirt-1.0.5
Doc Type: Enhancement
Doc Text:
Clone Of:
Environment:
Last Closed: 2014-06-13 11:58:27 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Description Daniel Berrangé 2012-08-22 08:42:42 UTC 
Description of problem:
The depth of the cgroup heirarchy can have performance implications. Libvirt currently creates a hierarchy 3 to 4 levels deep below the cgroup that libvirtd itself is placed in.

  libvirt/$DRIVERNAME/$VMNAME/$VCPUNUM

The first level is potentially redundant if systemd is already placing libvirtd in a private cgroup. The second and third levels could be optionally combined into '$DRIVERNAME-$VMNAME' 

There could be back compatibility issues with changing this, and potentially different scenarios will need different arrangements. Thus the layout probably ought to be made configuration, using placeholders eg

 1. Match current hardcoded layout:

    cgroup_layout="::PROCESS::/libvirt/::DRIVER::/::VMNAME::" 

 2. Remove first level when used with systemd:

    cgroup_layout="::PROCESS::/::DRIVER::/::VMNAME::" 

 3. Ignore current libvirtd placement completely and create in the root:

    cgroup_layout="/libvirt/::DRIVER::/::VMNAME::"

 4. Combine 2nd and 3rd levels

    cgroup_layout="/libvirt/::DRIVER::-::VMNAME::"

 5. Combine 2nd and 3rd levels, but use UUID instead of VM name

    cgroup_layout="/libvirt/::DRIVER::-::VMUUID::"

etc
Comment 1 Daniel Berrangé 2013-07-02 14:25:01 UTC 
Resolved with the introduction of the new cgroups layout in libvirt

http://libvirt.org/cgroups.html
Comment 2 yanbing du 2013-11-11 09:16:02 UTC 
# rpm -q libvirt
libvirt-1.1.1-11.el7.x86_64

Start 2 guests(named: virt-tests-vm and test), then check the cgroup layout:

# lscgroup 
cpuset:/
cpuset:/machine.slice
cpuset:/machine.slice/machine-qemu\x2dtest.scope
cpuset:/machine.slice/machine-qemu\x2dtest.scope/emulator
cpuset:/machine.slice/machine-qemu\x2dtest.scope/vcpu0
cpuset:/machine.slice/machine-qemu\x2dvirt\x2dtests\x2dvm.scope
cpuset:/machine.slice/machine-qemu\x2dvirt\x2dtests\x2dvm.scope/emulator
cpuset:/machine.slice/machine-qemu\x2dvirt\x2dtests\x2dvm.scope/vcpu0
cpu,cpuacct:/
cpu,cpuacct:/machine.slice
cpu,cpuacct:/machine.slice/machine-qemu\x2dtest.scope
cpu,cpuacct:/machine.slice/machine-qemu\x2dtest.scope/emulator
cpu,cpuacct:/machine.slice/machine-qemu\x2dtest.scope/vcpu0
cpu,cpuacct:/machine.slice/machine-qemu\x2dvirt\x2dtests\x2dvm.scope
cpu,cpuacct:/machine.slice/machine-qemu\x2dvirt\x2dtests\x2dvm.scope/emulator
cpu,cpuacct:/machine.slice/machine-qemu\x2dvirt\x2dtests\x2dvm.scope/vcpu0
memory:/
memory:/machine.slice
memory:/machine.slice/machine-qemu\x2dtest.scope
memory:/machine.slice/machine-qemu\x2dvirt\x2dtests\x2dvm.scope
devices:/
devices:/machine.slice
devices:/machine.slice/machine-qemu\x2dtest.scope
devices:/machine.slice/machine-qemu\x2dvirt\x2dtests\x2dvm.scope
freezer:/
freezer:/machine.slice
freezer:/machine.slice/machine-qemu\x2dtest.scope
freezer:/machine.slice/machine-qemu\x2dvirt\x2dtests\x2dvm.scope
net_cls:/
net_cls:/machine.slice
net_cls:/machine.slice/machine-qemu\x2dtest.scope
net_cls:/machine.slice/machine-qemu\x2dvirt\x2dtests\x2dvm.scope
blkio:/
blkio:/machine.slice
blkio:/machine.slice/machine-qemu\x2dtest.scope
blkio:/machine.slice/machine-qemu\x2dvirt\x2dtests\x2dvm.scope
perf_event:/
perf_event:/machine.slice
perf_event:/machine.slice/machine-qemu\x2dtest.scope
perf_event:/machine.slice/machine-qemu\x2dvirt\x2dtests\x2dvm.scope
hugetlb:/


# ll /sys/fs/cgroup/systemd/
total 0
-rw-r--r--.  1 root root 0 Nov  6 14:59 cgroup.clone_children
--w--w--w-.  1 root root 0 Nov  6 14:59 cgroup.event_control
-rw-r--r--.  1 root root 0 Nov  6 14:59 cgroup.procs
-r--r--r--.  1 root root 0 Nov  6 14:59 cgroup.sane_behavior
drwxr-xr-x.  4 root root 0 Nov 11 16:23 machine.slice
-rw-r--r--.  1 root root 0 Nov  6 14:59 notify_on_release
-rw-r--r--.  1 root root 0 Nov  6 14:59 release_agent
drwxr-xr-x. 78 root root 0 Nov 11 16:50 system.slice
-rw-r--r--.  1 root root 0 Nov  6 14:59 tasks
drwxr-xr-x.  3 root root 0 Nov  6 14:59 user.slice

# ll /sys/fs/cgroup/systemd/machine.slice/
total 0
-rw-r--r--. 1 root root 0 Nov  6 15:10 cgroup.clone_children
--w--w--w-. 1 root root 0 Nov  6 15:10 cgroup.event_control
-rw-r--r--. 1 root root 0 Nov  6 15:10 cgroup.procs
drwxr-xr-x. 2 root root 0 Nov 11 17:12 machine-qemu\x2dtest.scope
drwxr-xr-x. 2 root root 0 Nov 11 16:24 machine-qemu\x2dvirt\x2dtests\x2dvm.scope
-rw-r--r--. 1 root root 0 Nov  6 15:10 notify_on_release
-rw-r--r--. 1 root root 0 Nov  6 15:10 tasks
Comment 3 Ludek Smid 2014-06-13 11:58:27 UTC 
This request was resolved in Red Hat Enterprise Linux 7.0.

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