lkml.org 
[lkml]   [2017]   [Sep]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 3/4] paravirt: add virt_spin_lock pvops function
From
Date
On 09/06/2017 09:06 AM, Peter Zijlstra wrote:
> On Wed, Sep 06, 2017 at 08:44:09AM -0400, Waiman Long wrote:
>> On 09/06/2017 03:08 AM, Peter Zijlstra wrote:
>>> Guys, please trim email.
>>>
>>> On Tue, Sep 05, 2017 at 10:31:46AM -0400, Waiman Long wrote:
>>>> For clarification, I was actually asking if you consider just adding one
>>>> more jump label to skip it for Xen/KVM instead of making
>>>> virt_spin_lock() a pv-op.
>>> I don't understand. What performance are you worried about. Native will
>>> now do: "xor rax,rax; jnz some_cold_label" that's fairly trival code.
>> It is not native that I am talking about. I am worry about VM with
>> non-Xen/KVM hypervisor where virt_spin_lock() will actually be called.
>> Now that function will become a callee-saved function call instead of
>> being inlined into the native slowpath function.
> But only if we actually end up using the test-and-set thing, because if
> you have paravirt we end up using that.

I am talking about scenario like a kernel with paravirt spinlock running
in a VM managed by VMware, for example. We may not want to penalize them
while there are alternatives with less penalty.

Cheers,
Longman

\
 
 \ /
  Last update: 2017-09-06 15:11    [W:0.051 / U:0.084 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site