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

David Miller
2016-10-21T14:57:31Z

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.