Re: [PATCH] arm64: KVM: Save two instructions in __guest_enter()

[Shanker Donthineni]

Hi Christoffer,

This is change may not provide the measurable performance improvement, 
but still we can
save a few cpu cycles on vCPU context switch and also improves the code 
readability.


On 08/25/2016 08:31 AM, Christoffer Dall wrote:
> Hi Shanker,
>
> On Tue, Aug 09, 2016 at 08:15:36PM -0500, Shanker Donthineni wrote:
> > We are doing an unnecessary stack push/pop operation when restoring
> > the guest registers x0-x18 in __guest_enter(). This patch saves the
> > two instructions by using x18 as a base register. No need to store
> > the vcpu context pointer in stack because it is redundant and not
> > being used anywhere, the same information is available in tpidr_el2.
> Does this have any measureable benefit?
>
> Thanks,
> -Christoffer

--
Shanker Donthineni
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.