Setting Dom0 VCPU weight
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Hi,
I am having issue setting the VCPU weight for Dom0, I want to assign it a higher weight than other VMs, but the configuration does not seem to take effect. And when I re-check the weight on Dom0, it changes! Please see below:[06:45 xcp-ng-gqcbymae ~]# xl sched-credit Cpupool Pool-0: tslice=30ms ratelimit=1000us migration-delay=0us Name ID Weight Cap Domain-0 0 85 0 XOA 1 256 0 HP-VM-2 6 256 0 HP-VM-3 12 256 0 HP-VM-1 18 256 0 [06:45 xcp-ng-gqcbymae ~]# xl sched-credit -d 0 -w 512 [06:46 xcp-ng-gqcbymae ~]# xl sched-credit Cpupool Pool-0: tslice=30ms ratelimit=1000us migration-delay=0us Name ID Weight Cap Domain-0 0 85 0 XOA 1 256 0 HP-VM-2 6 256 0 HP-VM-3 12 256 0 HP-VM-1 18 256 0 [06:46 xcp-ng-gqcbymae ~]# xl sched-credit Cpupool Pool-0: tslice=30ms ratelimit=1000us migration-delay=0us Name ID Weight Cap Domain-0 0 85 0 XOA 1 256 0 HP-VM-2 6 256 0 HP-VM-3 12 256 0 HP-VM-1 18 256 0 [06:46 xcp-ng-gqcbymae ~]# xl sched-credit Cpupool Pool-0: tslice=30ms ratelimit=1000us migration-delay=0us Name ID Weight Cap Domain-0 0 170 0 XOA 1 256 0 HP-VM-2 6 256 0 HP-VM-3 12 256 0 HP-VM-1 18 256 0Can someone advise what else needs to be done? Thank you!
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Why do you want to do this in the first place? Also with XCP-ng, you shouldn't use
xlin general. It'sxethat you need. -
Thank you Olivier.
I am running some tests to verify the CPU weight actually takes priority under high load conditions. In our setup, there are some VMs that run mission critical high volume I/O services, I am able to set their CPU weight to 512. However, I need to make sure the Dom0 CPU weight stays at a higher priority than the guest VM's weight. In essence setting 3 priority tiers (1) Dom0 @1024, (2) High Priority service VMs @512, (3) low priority service VMs @256.
The xe command does not work on my setup:[13:41 xcp-ng-gqcbymae ~]# sudo xe sched-credit -d 0 -w 512 Syntax error: For usage run: 'xe help'The xl command works, but cannot change the priority for Dom0:
[13:42 xcp-ng-gqcbymae ~]# sudo xl sched-credit -d 0 -w 512 [13:45 xcp-ng-gqcbymae ~]# xl sched-credit Cpupool Pool-0: tslice=30ms ratelimit=1000us migration-delay=0us Name ID Weight Cap Domain-0 0 128 0 XOA 1 256 0 HP-VM-2 6 256 0 HP-VM-3 12 256 0 HP-VM-1 18 256 0The same command works well on guest VM #6 as follows:
[13:45 xcp-ng-gqcbymae ~]# sudo xl sched-credit -d 6 -w 512 [13:46 xcp-ng-gqcbymae ~]# xl sched-credit Cpupool Pool-0: tslice=30ms ratelimit=1000us migration-delay=0us Name ID Weight Cap Domain-0 0 64 0 XOA 1 256 0 HP-VM-2 6 512 0 HP-VM-3 12 256 0 HP-VM-1 18 256 0Does the VM with 512 weight have a higher priority than Dom0 under load conditions in this case? Or does Dom0 always get higher regardless of what is shown here? It seems the weight metric keeps changing for Dom0 by itself.
Thanks!
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Okay so sorry if I wasn't clear:
xeisn't a 1:1 replacement forxl. It's a complete/dedicated API that you have on XenServer and XCP-ng (it's called XAPI).The design is simple: XAPI first. You must find how to do that with XAPI if possible, because if you do with
xe, it might not be saved becausexlconfig aren't saved in a database, unlike XAPI withxe -
Thanks Olivier. Yes I am able to set the parameter now using xe commands. Thanks for your help!
