Re: [Qemu-ppc] Adding canyonlands/460EX support to QEMU in qemu-system-ppc

[Alexander Graf]

On 25.02.2013, at 17:11, Allen Kneser wrote:

Hi Alexander,

Thank you for your help! This is quite useful!

Pardon my lack of expertise, but what do you mean by KVM being available for canyonlands? I am actually trying to emulate this PowerPC board on an x86_64 PC, and my understanding is that I cannot benefit from KVM virtualization in this setup because of the architecture difference. 

Correct. But if you have a canyonlands board you can run KVM on that one and execute a lot of the instructions natively.

On a related note, my performance is not great at all:

QEMU bamboo sysbench CPU test:

      total time:                          10.3413s

      total number of events:              9

      total time taken by event execution: 10.2956

AMCC canyonlands sysbench CPU test:

      total time:                          10.0043s

      total number of events:              621

      total time taken by event execution: 10.0032

Core 2 Duo P8700 @ 2.53Ghz sysbench CPU test:

      total time:                          9.6486s

      total number of events:              10000

      total time taken by event execution: 9.6338

Is this to be expected? Would you have any suggestions on how to improve performance? 

There is a profile switch to configure that can tell you at least roughly where your performance drops originate from. IIRC BookE was doing excessive virtual tlb flushing. I tried to reduce that a while ago, but didn't succeed without breaking the guest :).

So yes, for now this is expected.

Would adding the 460EX with FP CPU to QEMU improve performance?

There are already with-FP and without-FP 440 CPUs available. Emulating 460 won't make any difference in speed.

Would the performance increase drastically by running the VM on a PowerPC machine with KVM support on the host and the guest?

Yes :). Even though page faults are quite expensive on 440 compared to e500. But it's a dramatic step up from TCG.

Alex