[pve-devel] KVM with same cores as host is as slow as one core
Stefan Priebe - Profihost AG
s.priebe at profihost.ag
Fri Jul 19 10:53:11 CEST 2013
Am 19.07.2013 09:22, schrieb Alexandre DERUMIER:
> What are the physical processors ? (Is it an numa architecture ? if yes, could be a memory bandwith problem)
> Do you have tried to launch unixbench on the host to compare ?
> Maybe can you try to add +x2apic cpu flag ? It should reduce interrupts. (It's already in current qemu-server git)
Sorry ignore me. This seems to be a known bug:
> ----- Mail original -----
> De: "Stefan Priebe - Profihost AG" <s.priebe at profihost.ag>
> À: pve-devel at pve.proxmox.com
> Envoyé: Vendredi 19 Juillet 2013 09:07:27
> Objet: [pve-devel] KVM with same cores as host is as slow as one core
> while benchmarking my kvm machines using unixbench i see the following
> reproducable behaviour.
> Host has 24 cores.
> KVM Machine set to 2 cores: Unixbench Value 2514
> KVM Machine set to 16 cores: Unixbench Value 6714
> KVM Machine set to 24 cores: Unixbench Value 1742
> Also i see a max of 105% CPU Usage of the KVM process when setting the
> cores to 24.
> While i'm seeing more than 1000% setting it to 16 cores.
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