> -----Original Message----- > From: Avi Kivity [mailto:avi@xxxxxxxxxx] > Sent: Thursday, September 27, 2012 6:12 PM > To: Hao, Xudong > Cc: kvm@xxxxxxxxxxxxxxx; Zhang, Xiantao > Subject: Re: [PATCH v4] kvm/fpu: Enable fully eager restore kvm FPU > > On 09/26/2012 07:54 AM, Hao, Xudong wrote: > >> -----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? > > Why not make it eager all the time then? It will simplify the code > quite a bit, no? > The code will simple if make it eager, I'll remove the lazy logic. -- 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
