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Re: [Xen-users] Release 0.8.9 of GPL PV drivers for Windows

On Mon, May 05, 2008 at 08:32:46PM -0400, jim burns wrote:

> - dom0 vs. domu: obviously, the standard to match is dom0 performance. (I 
> suspect, tho', that non-xen kernel performance would be even better.) Looking 
> at the 4k pattern numbers above, hvm severely lags dom0. Interestingly 
> enough, for the 32k pattern, hvm is doing better than dom0.

domU doing better than dom0 usually happens when you use file backed disks on
dom0.. then the memory cache of dom0 will affect the domU results. 
> > Could you try iometer on dom0 to see what kind of performance you get
> > there.. or on linux pv domU?
> As you can see above, I did do dom0. I could do a linux pv, but your next 
> idea 
> interests me more.

OK. I think measuring pv domU is worth trying too :)

> > And one more thing.. was your XP HVM single vcpu or more? Did you try
> > binding both dom0 and hvm domU to their own dedicated cpu cores?
> It was vcpu=2.

I think you should re-test with vcpu=1. 

Configure dom0 for 1 vcpu and domU for 1 vcpu and pin the domains to have a 
dedicated core. This way you're not sharing any pcpu's between the domains.
I think this is the "recommended" setup from xen developers for getting
maximum performance. 

I think the performance will be worse when you have more vcpus in use than
your actual pcpu count.. 

> Yeeaaahh - everything tanked! MB/s down, Cpu % up, etc. Console was still a 
> little sluggish. (I suppose pinning cpus might work better with more than one 
> socket on the mobo.) I won't be trying that config again ;-)

Hmm.. interesting. Maybe it was because of the shared pcpu's.. 

-- Pasi

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