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

[Janusz Ulanowski <janul666@xxxxxxxxx>]

Hi,
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 ?
Thanks
Janusz


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
>
>  
>
> Thanks
>
> -Padma
>
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> -----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>
>
> http://www.cmdln.org
>
> http://www.anders0n.net

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