[Qemu-devel] Testing migration under stress

[David Gibson <david@gibson.dropbear.id.au>]

Asking for some advice on the list.

I have prorotype savevm and migration support ready for the pseries
machine.  They seem to work under simple circumstances (idle guest).
To test them more extensively I've been attempting to perform live
migrations (just over tcp->localhost) which the guest is active with
something.  In particular I've tried while using octave to do matrix
multiply (so exercising the FP unit) and my colleague Alexey has tried
during some video encoding.

However, in each of these cases, we've found that the migration only
completes and the source instance only stops after the intensive
workload has (just) completed.  What I surmise is happening is that
the workload is touching memory pages fast enough that the ram
migration code is never getting below the threshold to complete the
migration until the guest is idle again.

Does anyone have some ideas for testing this better: workloads that
are less likely to trigger this behaviour, or settings to tweak in the
migration itself to make it more likely to complete migration while
the workload is still active.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson