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Re: [PATCH/RFC 0/5] cpu_relax: introduce yield, remove lowlatency

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On 10/21/2016 04:57 PM, David Miller wrote:
> From: Christian Borntraeger <borntraeger@de.ibm.com>
> Date: Fri, 21 Oct 2016 13:58:53 +0200
> 
>> For spinning loops people did often use barrier() or cpu_relax().
>> For most architectures cpu_relax and barrier are the same, but on
>> some architectures cpu_relax can add some latency. For example on s390
>> cpu_relax gives up the time slice to the hypervisor. On power cpu_relax
>> tries to give some of the CPU to the neighbor threads. To reduce the
>> latency another variant cpu_relax_lowlatency was introduced. Before this
>> is used in more and more places, lets revert the logic of provide a new
>> function cpu_relax_yield that can spend some time and for s390 yields
>> the guest CPU.
> 
> Sparc64, fwiw, behaves similarly to powerpc.

As sparc currently defines cpu_relax_lowlatency to cpu_relax, this patch set
should be a no-op then for sparc, correct?

My intend was that cpu_relax should not add a huge latency but can certainly
push some cpu power to hardware threads of the same core. This seems to be
the case for sparc/power and some arc variants. 

Christian

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[PATCH/RFC 0/5] cpu_relax: introduce yield, remove lowlatency Christian Borntraeger <borntraeger@de.ibm.com> - 2016-10-21 14:10 +0200
  [PATCH 1/5] processor.h: introduce cpu_relax_yield Christian Borntraeger <borntraeger@de.ibm.com> - 2016-10-21 14:10 +0200
  [PATCH 4/5] Remove cpu_relax_lowlatency users Christian Borntraeger <borntraeger@de.ibm.com> - 2016-10-21 14:10 +0200
  Re: [PATCH/RFC 0/5] cpu_relax: introduce yield, remove lowlatency Peter Zijlstra <peterz@infradead.org> - 2016-10-21 14:10 +0200
  Re: [PATCH/RFC 0/5] cpu_relax: introduce yield, remove lowlatency David Miller <davem@davemloft.net> - 2016-10-21 17:00 +0200
    Re: [PATCH/RFC 0/5] cpu_relax: introduce yield, remove lowlatency Christian Borntraeger <borntraeger@de.ibm.com> - 2016-10-21 17:10 +0200
      Re: [PATCH/RFC 0/5] cpu_relax: introduce yield, remove lowlatency David Miller <davem@davemloft.net> - 2016-10-21 17:20 +0200

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