RE: [Xen-users] Machine time delay in guest domains (Fullvirtualization)

[Caz Yokoyama <cazyokoyama@xxxxxxxxx>]

Hello Goto-san,

"SPEC CPU2006" probably refers domain virtual time. Let’s assume you have one Dom0 and 2 DomUs and each one is scheduled 1/3 of processor time. Each one receives 33 clock ticks out of 100 clock ticks. Domain virtual time of DomU is advanced 1/3 of actual clock (wall clock time). Please refer “2.4 Time” of “Xen Interface manual Xen v3.0 for x86” for detail.

 

Thank you.

-Caz Yokoyama, caz@xxxxxxxxxxx, CazYokoyama@xxxxxxxxx, +1-503-804-1028(m)

---

From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of KUMIKO GOTO
Sent: Thursday, December 27, 2007 7:49 AM
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Machine time delay in guest domains (Fullvirtualization)

 

Hi,

I have one question about machine time delay in guest domains (full
virtualization).

In order to evaluate cpu performance, I applied "SPEC CPU2006" and found
that
machine time of guest domains is severely delayed from actual time.
->Actual test time : test time measured in guest domains = 4:1
(e.g., Actual test time =40 min, test time measured in guest domain time
=10 min)

I think that there is some relationship between the number of domains and
cores.
(please see the following results)

Does anyone know why this kind of time delay occurs in Xen?

------------------------------------------------------
<<Environment>>
-Host machine has 2 cores (core number 0-1)
-Guest OSs: Full virtualization

*test 1
4 domains share 2 core (each domain has 2 vcpu)
->result: actual test time : test time measured in guest domains = 4:1

*test 2
2 domains share 1 core and the other 2 domains share the other 1 core.
->result: actual test time : test time measured in guest domains = 2:1
------------------------------------------------------

Thanks for your kindness.

Best,

-Kumiko

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