lkml.org 
[lkml]   [2017]   [Aug]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC] KVM: optimize the kvm_vcpu_on_spin
From
Date
On 01/08/2017 05:26, Longpeng (Mike) wrote:
>
>
> On 2017/7/31 21:20, Paolo Bonzini wrote:
>
>> On 31/07/2017 14:27, David Hildenbrand wrote:
>>>> I'm not sure whether the operation of get the vcpu's priority-level is
>>>> expensive on all architectures, so I record it in kvm_sched_out() for
>>>> minimal the extra cycles cost in kvm_vcpu_on_spin().
>>>>
>>> as you only care for x86 right now either way, you can directly optimize
>>> here for the good (here: x86) case (keeping changes and therefore
>>> possible bugs minimal).
>>
>> I agree with Cornelia that this is inconsistent, so you shouldn't update
>> me->in_kernmode in kvm_vcpu_on_spin. However, get_cpl requires
>> vcpu_load on Intel x86, so Mike's patch is necessary (vmx_get_cpl ->
>> vmx_read_guest_seg_ar -> vmcs_read32).
>>
>
> Hi Paolo,
>
> It seems that other architectures(e.g. arm/s390) needn't to cache the result,
> but x86 need, so I need to move 'in_kernmode' into kvm_vcpu_arch and only add
> this field to x86, right?

That's another way to do it, and I like it.

>> This will cache the result until the next sched_in, so that
>
> 'until the next sched_in' --> Do we need to clear the result in sched in ?

No, thanks.

Paolo

\
 
 \ /
  Last update: 2017-08-01 10:33    [W:0.038 / U:0.236 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site