Re: (no subject)

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 13/02/14 16:01, Simon Martin wrote:
> Hi all,
>
> I  am  now successfully running my little operating system inside Xen.

Congratulations!

> It  is  fully  preemptive and working a treat, but I have just noticed
> something  I  wasn't expecting, and will really be a problem for me if
> I can't work around it.
>
> My configuration is as follows:
>
> 1.- Hardware: Intel i3, 4GB RAM, 64GB SSD.

Can you be more specific - this covers 4 generations of Intel CPUs.

>
> 2.- Xen: 4.4 (just pulled from repository)
>
> 3.- Dom0: Debian Wheezy (Kernel 3.2)
>
> 4.- 2 cpu pools:
>
> # xl cpupool-list
> Name               CPUs   Sched     Active   Domain count
> Pool-0               3    credit       y          2
> pv499                1  arinc653       y          1
>
> 5.- 2 domU:
>
> # xl list
> Name                                        ID   Mem VCPUs      State   Time(s)
> Domain-0                                     0   984     3     r-----      39.7
> win7x64                                      1  2046     3     -b----     143.0
> pv499                                        3   128     1     -b----      61.2
>
> 6.- All VCPUs are pinned:
>
> # xl vcpu-list
> Name                                ID  VCPU   CPU State   Time(s) CPU Affinity
> Domain-0                             0     0    0   -b-      27.5  0
> Domain-0                             0     1    1   -b-       7.2  1
> Domain-0                             0     2    2   r--       5.1  2
> win7x64                              1     0    0   -b-      71.6  0
> win7x64                              1     1    1   -b-      37.7  1
> win7x64                              1     2    2   -b-      34.5  2
> pv499                                3     0    3   -b-      62.1  3
>
> 7.- pv499 is the domU that I am testing. It has no disk or vif devices
> (yet). I am running a little test program in pv499 and the timing I
> see is varies depending on disk activity.
>
> My test program runs prints up the time taken in milliseconds for a
> million cycles. With no disk activity I see 940 ms, with disk activity
> I see 1200 ms.
>
> I can't understand this as disk activity should be running on cores 0,
> 1  and 2, but never on core 3. The only thing running on core 3 should
> by my paravirtual machine and the hypervisor stub.
>
> Any idea what's going on?

Curious.  Lets try ruling some things out.

How are you measuring time in pv499?

What is your Cstates and Pstates looking like?  If you can, try
disabling turbo?

~Andrew