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? All I was looking for was no regressions, a small speedup is just a bonus. -- error compiling committee.c: too many arguments to function -- 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
