Re: High vm-exit latencies during kvm boot-up/shutdown

Dong, Eddie
2007-10-26T09:18:48Z

Jan Kiszka wrote:
>
> So if you want the higher performance of PCIe you need
> performance-killing wbindv (not to speak of latency)? That sounds a
> bit contradictory to me. So this is also true for native PCIe usage?
>

Mmm, I won't say so. When you want to get RT performance, you
won't use unknown OS such as Windows. If you use your RT
linux, the OS (guest) itself should not use wbinvd.

For the Bochs BIOS case, like Avi mentioned, we can simply remove it.

> What really frightens me about wbinvd is that its latency "nicely"
> scales with the cache sizes. And I think my observed latency
> is far from
> being the worst case. In a different experiment, I once measured
> wbinvd latencies of a few milliseconds... :(
>
I don't know details, but it could be. While RT usage can easily remove
this instruction.

thx,eddie