RE: [Xen-devel] Performance issuses with Splash2 applications on XEN

[jessie smart <jessiesmart354@xxxxxxxxx>]

sorry it took so long for my response.......

I am not using the unstable XEN release - I am using XEN 2.0.1 <xen-2.0.1-src.tgz> installed on Fedora Core 3 using "make world" so that it downloads and builds it own kernel.

domU (1GB RAM) is booted from a file-backed VBD on a local HDD (I have tested this on a LVM-backed VBD over NFS and see no significant differences).

The splash applications that I am using, use the lpthread library. So when I refer to running an application with multiple processors, I am referring to multiple threads <this is how they call it>.

The splash applications use a LOT of synchronization objects during their operation (e.g., mutex and conditional variables). Other than that, they simply allocate memory and do a lot of mathematical computations (I.e., floating point).

Could the pthread library operations (I.e., pthread synchronization objects) be the cause of the performance hit within domain?

Hardware:

Tyan s2882 Motherboard

Dual 2.0 Ghz AMD Opteron

2GB of RAM

Broadcom GB NIC

 

 

Jessie Smart

jessiesmart354@xxxxxxxxx <mailto:jessiesmart354@xxxxxxxxx>

Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx> wrote:

Is this using SMP guests from the unstable tree? If so, there's some
serious scheduler issues which are currently being worked on -- its
certainly not ready for serious benchmarking (though this might be
useful application for us to use for tuning purposes).

How many CPUs has the machine you're running on? How many virtual CPUS
does the guest have?

Ian

> -----Original Message-----
> From: xen-devel-admin@xxxxxxxxxxxxxxxxxxxxx
> [mailto:xen-devel-admin@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of
> jessie smart
> Sent: 02 February 2005 20:23
> To: xen-devel@xxxxxxxxxxxxxxxxxxxxx
> Subject: [Xen-devel] Performance issuses with Splash2
> applications on XEN
>
> I am running one of the applications from the Stanford
> splash2 application suite (
> http://www-flash.stanford.edu/ap ps/ ) and getting an
> unexpected (~5x) performance decrease in domU when specifying
> more than 1 processor in the application. dom0 seems to
> handle this fine.
>
>
>
> Specificly I am seeing this on the water-nsquared app. I am
> not going to give my machine config here (if you need them
> please ask) just the differences in runtime and the
> parameters of the app.
>
>
>
>
>
> all are running single processor & 1GB RAM
>
> (times reported as real/user/system, in seconds)
>
>
>
> water-nsquared 64 processors 8000 molecules
>
>
>
> baseline (non-xen) 72.20/78.80/0.17
>
> Dom0 77.76/77.17/0.16
>
> DomU 357.24/357.04/0.018
>
>
>
> water-nsquared 1 processor 8000 molecules
>
>
>
> baseline (non-xen) 73.16/72.75/0.15
>
> Dom0 72.75/72.37/0.02
>
> DomU 66.07/66.04/0.02
>
>
>
>
>
> I have disabled the /lib/tls.
>
>
>
> I am hoping that someone here with a little more experience
> with Xen can help me try to explain this. Any input would be
> greatly appreciated.
>
>
>
> Jessie
>
> jessiesmart354@xxxxxxxxx
>
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