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Bug 1294475 - libvirt start vm under incorrect NUMA memory mode
Summary: libvirt start vm under incorrect NUMA memory mode
Keywords:
Status: CLOSED NOTABUG
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: libvirt
Version: 7.2
Hardware: x86_64
OS: Linux
unspecified
medium
Target Milestone: rc
: ---
Assignee: Michal Privoznik
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2015-12-28 11:41 UTC by Artyom
Modified: 2016-01-05 08:00 UTC (History)
4 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2016-01-04 13:39:43 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Description Artyom 2015-12-28 11:41:43 UTC 
Description of problem:
I start vm under NUMA memory strict mode, but when I check vm process numa_maps I can see that process run under prefer mode.

Version-Release number of selected component (if applicable):
# cat /etc/redhat-release 
Red Hat Enterprise Linux Server release 7.2 (Maipo)
# uname -r
3.10.0-327.el7.x86_64
# rpm -qa | grep libvirt
libvirt-client-1.2.17-13.el7_2.2.x86_64
libvirt-daemon-config-nwfilter-1.2.17-13.el7_2.2.x86_64
libvirt-daemon-driver-lxc-1.2.17-13.el7_2.2.x86_64
libvirt-lock-sanlock-1.2.17-13.el7_2.2.x86_64
libvirt-daemon-driver-nwfilter-1.2.17-13.el7_2.2.x86_64
libvirt-daemon-driver-interface-1.2.17-13.el7_2.2.x86_64
libvirt-daemon-config-network-1.2.17-13.el7_2.2.x86_64
libvirt-daemon-1.2.17-13.el7_2.2.x86_64
libvirt-daemon-driver-storage-1.2.17-13.el7_2.2.x86_64
libvirt-daemon-driver-network-1.2.17-13.el7_2.2.x86_64
libvirt-1.2.17-13.el7_2.2.x86_64
libvirt-daemon-kvm-1.2.17-13.el7_2.2.x86_64
libvirt-daemon-driver-secret-1.2.17-13.el7_2.2.x86_64
libvirt-daemon-driver-qemu-1.2.17-13.el7_2.2.x86_64
libvirt-python-1.2.17-2.el7.x86_64
libvirt-daemon-driver-nodedev-1.2.17-13.el7_2.2.x86_64

How reproducible:
Always

Steps to Reproduce:
1. Start vm under numa strict mode:
<numatune>
    <memory mode='strict' nodeset='0,2'/>
</numatune>
2. check numa_maps under vm process
# cat /proc/14328/numa_maps | head -n 1
7fb2677fa000 prefer:2

Actual results:
vm process run under prefer mode

Expected results:
vm process run under bind mode

Additional info:
Comment 2 Michal Privoznik 2016-01-04 13:39:43 UTC 
This is deliberate. Problem is, if we run it strictly under configured nodes there would be no way how to change it afterwards on a running guest. Therefore, libvirt - just before spawning qemu process - calls numa APIs to set affinity only in preferred mode and uses cgroups to enforce the strictness. See bug 1198645 or upstream commit ea576ee543d6fb955 for more info.
Comment 3 Artyom 2016-01-05 08:00:29 UTC 
Thanks for explanation, I will check bug 1198645.
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