Hi all,
while working on NUMA host pinning, I experimented with vCPU affinity
within QEMU, but left it alone as it would complicate the code and would
not achieve better experience than using taskset with the monitor
provided thread ids like it is done currently. During that I looked at
Linux' CPUSET implementation
(/src/linux-2.6/Documentation/cgroups/cpusets.txt).
In brief, this is a pseudo file system based, truly hierarchical
implementation of restricting a set of processes (or threads, it uses
PIDs) to a certain subset of the machine.
Sadly we cannot leverage this for true guest NUMA memory assignment, but
it would work nice for pinning (or not) guest vCPUs. I had the following
structure in mind:
For each guest there is a new CPUSET (mkdir $CPUSET_MNT/`cat
/proc/$$/cpuset`/kvm_$guestname). One could then assign the guest global
resources to this CPUSET.
For each vCPU there is a separate CPUSET located under this guest global
one. This would allow for easy manipulation of the pinning of vCPUs,
even from the console without any mgt app (although this could be easily
implemented in libvirt).
/
|
+--/ kvm_guest_01
| |
| +-- VCPU0
| |
| +-- VCPU1
|
+--/ kvm_guest_02
...
What do you think about it? It is worth implementing this?
Regards,
Andre.
--
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 448-3567-12
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