Re: [Xen-devel] [PATCH v2] x86: use VMLOAD for PV context switch

2018-09-11 Thread Boris Ostrovsky
On 9/11/18 10:38 AM, Jan Beulich wrote: On 11.09.18 at 16:17, wrote: >> On 9/11/18 3:54 AM, Jan Beulich wrote: >> On 10.09.18 at 23:56, wrote: On 09/10/2018 10:03 AM, Jan Beulich wrote: > Having noticed that VMLOAD alone is about as fast as a single of the > involved WRMSRs,

Re: [Xen-devel] [PATCH v2] x86: use VMLOAD for PV context switch

2018-09-11 Thread Jan Beulich
>>> On 11.09.18 at 16:17, wrote: > On 9/11/18 3:54 AM, Jan Beulich wrote: > On 10.09.18 at 23:56, wrote: >>> On 09/10/2018 10:03 AM, 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 al

Re: [Xen-devel] [PATCH v2] x86: use VMLOAD for PV context switch

2018-09-11 Thread Boris Ostrovsky
On 9/11/18 3:54 AM, Jan Beulich wrote: On 10.09.18 at 23:56, wrote: >> On 09/10/2018 10:03 AM, 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, howe

Re: [Xen-devel] [PATCH v2] x86: use VMLOAD for PV context switch

2018-09-11 Thread Jan Beulich
>>> On 10.09.18 at 23:56, wrote: > On 09/10/2018 10:03 AM, 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 c

Re: [Xen-devel] [PATCH v2] x86: use VMLOAD for PV context switch

2018-09-10 Thread Boris Ostrovsky
On 09/10/2018 10:03 AM, 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 with an early pre

[Xen-devel] [PATCH v2] x86: use VMLOAD for PV context switch

2018-09-10 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