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Re: [Xen-users] DomU slower with smp?

I have 4 QuadCore cpus.
I've done as you said and no difference. I missed my file with all results (I do again).
Also when I was increasing number of cpus for DomU I got worse result.
"xm vcpu-list 0" always shown me the same running vcpu: something like that:
xm vcpu-list 0
Name ID VCPU CPU State Time(s) CPU Affinity
Domain-0                             0     0     0   -b-     366.6 0
Domain-0                             0     1     1   r--    1068.2 1
Domain-0                             0     2     2   -b-    1629.7 2
Domain-0                             0     3     3   -b-    1410.6 3
I'm a bit confused about numbering cpus. doesn't it matter what `cat /proc/cpuinfo |grep ^core` in Dom0 shows ?


Apparao, Padmashree K wrote:

Here's one more suggestion

·        Try interrupt binding. Find out the irq of the nic/IO device

Now affinitize the interrupts to a particular cpu (usually 0)

Turn off interrupt balancing in Xen

Service Irq balance stop (in linux). There is a config parameter in Xen.

·        Xm vcpu-set 0 2

·        Xm vcpu-pin 0 0 0

·        Xm vcpu-pin 0 1 2

·        Now start your smp (with 4 vcpus) domU (say domid 2)

·        Xm vcpu-pin 2 0  1

·        Xm vcpu-pin 2 1 3

·        Xm vcpu-pin 2 2 5

·        Xm vcpu-pin 2 3 7

· Typically the cpus are numbered as cores 0,2, 4 and 6 on 1 die (1 quad core) and the cores 1,3,5,7 on another die. You want to separate the domU from dom0 altogether. Also by putting the domU on a different die you will eliminate any cache corruption.

· · I am not familiar with how the AMD machines enumerate the cores but this is how the Intel machines do.

· Can you please run this config and let us know what the thruput is. Similarly you can run the domU with 1 vcpu and bind it to one of the cores.

·        Also observe what the cpu% is for dom0 and domU.

I hope this helps. I am interested in seeing the data on this



-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Nick Anderson
Sent: Thursday, May 15, 2008 5:46 PM
To: Luke S Crawford
Cc: Janusz Ulanowski; xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] DomU slower with smp?

Luke S Crawford wrote:

> "Janusz Ulanowski" <janul666@xxxxxxxxx> writes:


>> I just made simple peformance test with iozone tool on xen 3.2.1.

> ...

>> It seems DomU  is much slower if using more than one cpu.

Its a dual socket quad core amd. So I have 8 cores. cpus for dom0 is set

to 0 and according to xend-config.sxp that will give dom0 access to all

cpus. I havent adjusted any weighting so im not sure what would be

stepping on it. The only thing running during the test was that one

domU. and the domU was idle when running the test on dom0.


Nick Anderson <nick@xxxxxxxxxxxx>



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