Xen vcpu allocation bug?

I found a lot of domains having the same physical CPU as multiple VCPUs.
so I guess each of them would have less performance available then expected? Or maybe this is the final victim of the f*****ing bug that everything gets stuck in state “b” which noone bothered to repair in 5 years.

Name   VCPU CPU State Time(s) CPU Affinity
Domain-0 0 2 r-- 213764.7 any cpu
Domain-0 1 5 -b- 36841.4 any cpu
Domain-0 2 4 -b- 34805.8 any cpu
Domain-0 3 6 -b- 27806.7 any cpu
Domain-0 4 1 -b- 27067.0 any cpu
Domain-0 5 7 -b- 25176.3 any cpu
Domain-0 6 2 -b- 23449.0 any cpu
Domain-0 7 0 -b- 28618.3 any cpu

2 thoughts on “Xen vcpu allocation bug?

  1. b state does nothing anyways so there should be no performance loss as nothing has to be performed. I think you should worry when they both become r state.
    nice blog, pleasure to read

  2. hi,

    always glad to hear this stuff is something people wanna read 🙂
    iirc the “b” state shows regardless of activity on the vcpu unless it’s the also in use by dom0 at the same time.
    there’s some ugly bug in there that noone fully understands.
    give it a try and run something like boinc on each core of a VM and see if you find all showing the “r” state. AFAIK it does never happen.
    Besides I still don’t see why a VM would ever be allocated the same vcpu twice.
    I won’t dig into it any more though, I need a more current box with 4.1 and “xl” to know I get reliable results.

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