> -----Original Message----- > From: kvm-owner@xxxxxxxxxxxxxxx [mailto:kvm-owner@xxxxxxxxxxxxxxx] On > Behalf Of Avi Kivity > Sent: Tuesday, September 25, 2012 4:16 PM > To: Hao, Xudong > Cc: kvm@xxxxxxxxxxxxxxx; Zhang, Xiantao > Subject: Re: [PATCH v4] kvm/fpu: Enable fully eager restore kvm FPU > > On 09/25/2012 04:32 AM, Hao, Xudong wrote: > > > > > > btw, it is clear that long term the fpu will always be eagerly loaded, > > > as hosts and guests (and hardware) are updated. At that time it will > > > make sense to remove the lazy fpu code entirely. But maybe that time is > > > here already, since exits are rare and so the guest has a lot of chance > > > to use the fpu, so eager fpu saves the #NM vmexit. > > > > > > Can you check a kernel compile on a westmere system? If eager fpu is > > > faster there than lazy fpu, we can just make the fpu always eager and > > > remove quite a bit of code. > > > > > I remember westmere does not support Xsave, do you want performance of > fxsave/fresotr ? > > Yes. If a westmere is fast enough then we can probably justify it. If > you can run tests on Sandy/Ivy Bridge, even better. > Run kernel compile on westmere, eager fpu is about 0.4% faster, seems eager does not benefit it too much, so remain lazy fpu for lazy_allowed fpu state? -Xudong -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
