On 2 Mar 2011 at 22:10, Peter Hjalmarsson wrote: > > > KVM is a different story, and I do see slowdown for amd64. > > > > this means that the slowdown is truly specific to some kvm/uderef > > interaction, > > not that i have an idea where to look still... > > Are you missing anything you need to figure this out, like profiling > data?
well, i've tried profiling with another user already but there was no conclusive data as to what could be the cause of the slowdown. it seems to be related to the generation of lots of extra page faults, something i'd even understand for UDEREF, but it also happens with KERNEXEC which is a mystery. also it seems to depend on the number of host CPUs, i could never really reproduce the slowdown on 2 cores, but it always occurs on 3+ host cores. i guess at this point someone familiar with KVM internals would have to be asked about this issue...
