Re: [Xen-users] Xen is 37x slower in processing a loop

[Fabian Zimmermann <xenusers@xxxxxxxxxxxxxxxxx>]

Hi

2011/12/25 Florian Heigl <florian.heigl@xxxxxxxxx>:
> please start by doing the comparisms using the same system, and then
> look into different domU kernels.

Quite hard, because the affected system is running prod. services.

FYI: I didn't run the tests in DomU, I tested Dom0!

> This, for example is on my irc VM, running 2.6.26-2 debian kernel on a
> squeeze host.
> The VM is actually even cpu capped to 70% of one i7 core.

But here the tests done in DomU:

DomU - Squeeze 2.6.32-5-xen-686

real    1m3.636s
user    0m1.192s
sys     1m3.356s

DomU - Etch 2.6.18-6-xen-686

real    0m48.190s
user    0m0.208s
sys     0m47.271s

> If it's taking 40s(!) for you then start looking for disk trashing in
> the host, too.
> i.e. md_resync used to completely abuse servers while it was running.

Host is powered by (real) hardware-raid, so md_resync is impossible.
Also checked io-usage, but nothing strange here. Also limited prio of
DomU-io-processes in Dom0 to IDLE, didn't help.

I think I have to reproduce this on different hardware to get this solved.

Any further hints would be nice.

Thanks a lot,

Fabian

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