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

[Alexander Graf]

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