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Cause:
For 'restrictive' numatune, libvirt wasn't setting cpuset.mems on domain startup, which kind of defeats the purpose of the configuration knob.
Consequence:
Domain was not restricted to run on configured NUMA nodes.
Fix:
Simple.
Result:
Libvirt now sets up cpuset CGroup controller for 'restrictive' numatune mode even on domain startup, so domain runs on desired NUMA nodes from the beginning.
Description of problem:Wrong cpuset.mems cgroup is set when setting numa tuning with "restrictive" mode.
Version-Release number of selected component (if applicable):
# rpm -q libvirt qemu-kvm
libvirt-8.0.0-21.module+el8.9.0+19166+e262ca96.x86_64
qemu-kvm-6.2.0-35.module+el8.9.0+19166+e262ca96.x86_64
How reproducible:
100%
Steps to Reproduce:
1 Start a guest with below setting:
<numatune>
<memory mode="restrictive" nodeset="0"/>
</numatune>
2 Check cpuset.mems cgroup setting
# cat /sys/fs/cgroup/cpuset/machine.slice/machine-qemu\\x2d1\\x2dvm1.scope/libvirt/emulator/cpuset.mems
0-1
# cat /sys/fs/cgroup/cpuset/machine.slice/machine-qemu\\x2d1\\x2dvm1.scope/libvirt/vcpu0/cpuset.mems
0-1
# cat /sys/fs/cgroup/cpuset/machine.slice/machine-qemu\\x2d1\\x2dvm1.scope/libvirt/vcpu1/cpuset.mems
0-1
Actual results:
We could see that the cpuset.mems cgroup setting of the guest is different with numa tuning setting
Expected results:
With restrictive mode, the cpuset.mems cgroup setting should follow the numa tuning setting.
I think this is the same as RHEL-9 bug 2070380. Upstream it was fixed by the following commit:
commit 629282d8845407c1aff9a26f5dc026e15121f8cd
Author: Michal Prívozník <mprivozn>
AuthorDate: Fri Apr 1 14:30:05 2022 +0200
Commit: Michal Prívozník <mprivozn>
CommitDate: Thu Apr 7 12:12:11 2022 +0200
lib: Set up cpuset controller for restrictive numatune
The aim of 'restrictive' numatune mode is to rely solely on
CGroups to have QEMU running on configured NUMA nodes. However,
we were never setting the cpuset controller when a domain was
starting up. We are doing so only when
virDomainSetNumaParameters() is called (aka live pinning).
This is obviously wrong. Fortunately, fix is simple as
'restrictive' is similar to 'strict' - every location where
VIR_DOMAIN_NUMATUNE_MEM_STRICT occurs can be audited and
VIR_DOMAIN_NUMATUNE_MEM_RESTRICTIVE case can be added.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2070380
Signed-off-by: Michal Privoznik <mprivozn>
Reviewed-by: Ján Tomko <jtomko>
v8.3.0-rc1~138
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory (Moderate: virt:rhel and virt-devel:rhel security, bug fix, and enhancement update), and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHSA-2023:6980
Description of problem:Wrong cpuset.mems cgroup is set when setting numa tuning with "restrictive" mode. Version-Release number of selected component (if applicable): # rpm -q libvirt qemu-kvm libvirt-8.0.0-21.module+el8.9.0+19166+e262ca96.x86_64 qemu-kvm-6.2.0-35.module+el8.9.0+19166+e262ca96.x86_64 How reproducible: 100% Steps to Reproduce: 1 Start a guest with below setting: <numatune> <memory mode="restrictive" nodeset="0"/> </numatune> 2 Check cpuset.mems cgroup setting # cat /sys/fs/cgroup/cpuset/machine.slice/machine-qemu\\x2d1\\x2dvm1.scope/libvirt/emulator/cpuset.mems 0-1 # cat /sys/fs/cgroup/cpuset/machine.slice/machine-qemu\\x2d1\\x2dvm1.scope/libvirt/vcpu0/cpuset.mems 0-1 # cat /sys/fs/cgroup/cpuset/machine.slice/machine-qemu\\x2d1\\x2dvm1.scope/libvirt/vcpu1/cpuset.mems 0-1 Actual results: We could see that the cpuset.mems cgroup setting of the guest is different with numa tuning setting Expected results: With restrictive mode, the cpuset.mems cgroup setting should follow the numa tuning setting.