Re: [Qemu-devel] Re: KVM call agenda for Feb 9

Alexander Graf
2010-02-09T07:16:33Z

On 09.02.2010, at 07:56, Avi Kivity wrote:

> On 02/09/2010 03:28 AM, Chris Wright wrote:
>> Please send in any agenda items you are interested in covering.
>>
>
> hpet overhead on large smp guests
>
> I measured hpet consuming about a half a core's worth of cpu on an idle Windows 2008 R2 64-way guest. This is mostly due to futex contention, likely from the qemu mutex.
>
> Options:
> - ignore, this is about 1% of the entire system (but overhead might increase greatly if a workload triggers more hpet accesses)
> - push hpet into kernel, with virtio-net, virtio-blk, and kernel-hpet, there's little reason to exit into qemu

That sounds like a good idea to me. It'd make the hpet en par with the lapic as timing source concerning overhead.

> - rcuify/fine-grain qemu locks

And this should be done either way, but is probably not a short-term goal.

Alex