Re: [Xen-devel] Hypervisor crash(!) on xl cpupool-numa-split

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Tue, Feb 8, 2011 at 4:33 PM, Andre Przywara <andre.przywara@xxxxxxx> wrote:
> (XEN) cpu_disable_scheduler: Migrating d0v18 from cpu 24
> (XEN) cpu_disable_scheduler: Migrating d0v34 from cpu 24
> (XEN) cpu_disable_scheduler: Migrating d0v42 from cpu 24
> (XEN) cpu_disable_scheduler: Migrating d0v18 from cpu 25
> (XEN) cpu_disable_scheduler: Migrating d0v34 from cpu 25
> (XEN) cpu_disable_scheduler: Migrating d0v42 from cpu 25
> (XEN) cpu_disable_scheduler: Migrating d0v18 from cpu 26
> (XEN) cpu_disable_scheduler: Migrating d0v32 from cpu 26
> (XEN) cpu_disable_scheduler: Migrating d0v42 from cpu 26
> (XEN) cpu_disable_scheduler: Migrating d0v18 from cpu 27
> (XEN) cpu_disable_scheduler: Migrating d0v24 from cpu 27
> (XEN) cpu_disable_scheduler: Migrating d0v32 from cpu 27
> (XEN) cpu_disable_scheduler: Migrating d0v42 from cpu 27
> (XEN) cpu_disable_scheduler: Migrating d0v3 from cpu 28
> (XEN) cpu_disable_scheduler: Migrating d0v18 from cpu 28
> (XEN) cpu_disable_scheduler: Migrating d0v25 from cpu 28
> (XEN) cpu_disable_scheduler: Migrating d0v32 from cpu 28
> (XEN) cpu_disable_scheduler: Migrating d0v39 from cpu 28
> (XEN) cpu_disable_scheduler: Migrating d0v3 from cpu 29

Interesting -- what seems to happen here is that as cpus are disabled,
vcpus are "shovelled" in an accumulative fashion from one cpu to the
next:
* v18,34,42 start on cpu 24.
* When 24 is brought down, they're all migrated to 25; then when 25 is
brougth down, to 26, then to 27
* v24 is running on cpu 27, so when 27 is brought down, v24 is added to the mix
* v3 is running on cpu 28, so all of them plus v3 are shoveled onto cpu 29.

While that behavior may not be ideal, it should certainly be bug-free.

Another interesting thing to note is that the bug happened on pcpu 32,
but there were no advertised migrations from that cpu.

Andre, can you fold the attached patch into your testing?

Thanks for all your work on this.

 -George

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