[Xen-devel] [PATCH] x86: use VMLOAD for PV context switch

2018-07-10 Thread Jan Beulich
Having noticed that VMLOAD alone is about as fast as a single of the involved WRMSRs, I thought it might be a reasonable idea to also use it for PV. Measurements, however, have shown that an actual improvement can be achieved only with an early prefetch of the VMCB (thanks to Andrew for suggesting

Re: [Xen-devel] [PATCH] x86: use VMLOAD for PV context switch

2018-08-16 Thread Brian Woods
On Tue, Jul 10, 2018 at 04:14:11AM -0600, Jan Beulich wrote: > Having noticed that VMLOAD alone is about as fast as a single of the > involved WRMSRs, I thought it might be a reasonable idea to also use it > for PV. Measurements, however, have shown that an actual improvement can > be achieved only

Re: [Xen-devel] [PATCH] x86: use VMLOAD for PV context switch

2018-08-17 Thread Jan Beulich
>>> On 17.08.18 at 00:04, wrote: > On Tue, Jul 10, 2018 at 04:14:11AM -0600, Jan Beulich wrote: >> Having noticed that VMLOAD alone is about as fast as a single of the >> involved WRMSRs, I thought it might be a reasonable idea to also use it >> for PV. Measurements, however, have shown that an ac

Re: [Xen-devel] [PATCH] x86: use VMLOAD for PV context switch

2018-08-17 Thread Brian Woods
On Fri, Aug 17, 2018 at 01:33:43AM -0600, Jan Beulich wrote: > >>> On 17.08.18 at 00:04, wrote: > > On Tue, Jul 10, 2018 at 04:14:11AM -0600, Jan Beulich wrote: > >> Having noticed that VMLOAD alone is about as fast as a single of the > >> involved WRMSRs, I thought it might be a reasonable idea t

Re: [Xen-devel] [PATCH] x86: use VMLOAD for PV context switch

2018-08-17 Thread Jan Beulich
>>> On 17.08.18 at 16:55, wrote: > On Fri, Aug 17, 2018 at 01:33:43AM -0600, Jan Beulich wrote: >> >>> On 17.08.18 at 00:04, wrote: >> > On Tue, Jul 10, 2018 at 04:14:11AM -0600, Jan Beulich wrote: >> >> Having noticed that VMLOAD alone is about as fast as a single of the >> >> involved WRMSRs, I