[Xen-devel] multi-processor odd behavior?

[John L Griffin <jlg@xxxxxxxxxx>]

Hey folks,

I'm using a recent (dated last weekend) xen-unstable build on a machine 
with two processors.  (Well, one processor with hyperthreading turned on.)

I've created two guest domains.  Inside each domain, I have a simple 
application ("eat") that's a simple "for(;;);" loop, to consume as much 
CPU as possible.

I'm seeing odd behavior:

1. When I run "eat" inside one guest, "xm top" reports for CPU(%):

  Domain-0:  0.5
   guest-1: 99.6
   guest-2:  0.0

2. When I run "eat" inside both guests:

  Domain-0:  0.5
   guest-1: 49.9
   guest-2: 49.9

  [This isn't what I expect, which is for both domains to run near 100%.]

3. When I run "eat" inside both guests *and* in Domain-0:

  Domain-0: 97.6
   guest-1: 49.9
   guest-2: 49.9

This seems to indicate that one CPU is being reserved entirely for dom0, 
even when dom0 isn't using it to capacity?  (That doesn't seem like the 
intended behavior.)  Do I have a configuration option set wrong?  Or is 
this a known issue?  Or, is it fixed in the latest builds?

"xm top" shows "CPUs: 2 @ 2992MHz", and also indicates that Domain-0 has 2 
VCPUS while each of the guests has 1 VCPU.

Thanks,
JLG


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