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Re: Fwd: [PATCH] spinlock spin with pause instruction

From: VÃclav Haisman <vhaisman at gmail dot com>
To: cygwin-patches at cygwin dot com
Date: Sat, 12 Mar 2016 09:13:37 +0100
Subject: Re: Fwd: [PATCH] spinlock spin with pause instruction
Authentication-results: sourceware.org; auth=none
References: <CAKw7uVgrjqZVznRMoCbsjyz4YXast5YtAAmpWQorOw7YXqbOhw at mail dot gmail dot com> <CAKw7uVg78t2V8KKLYfPyhb97XjU+aUb4KV-poz7i_wwDeJ6b=g at mail dot gmail dot com> <56E3B674 dot 7020702 at maxrnd dot com>

On 12.3.2016 07:25, Mark Geisert wrote:
> Václav Haisman wrote:
>> Hi.
>>
>> I have noticed that Cygwin's spinlock goes into heavy sleeping code
>> for each spin. It seems it would be a good idea to actually try to
>> spin a bit first. There is this 'pause' instruction which let's the
>> CPU make such busy loops be less busy. Here is a patch to do this.
> 
> I wanted to try out this patch but compilation is failing on the
> "unlikely" call.  Is that a macro that needs defining or something else?
> Thanks,
> 
> ..mark
> 

`unlikely()` is a macro defined in `miscfuncs.h`, right below header
guard:
<https://cygwin.com/git/gitweb.cgi?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/miscfuncs.h;h=3a9f0258c6cbb62b8d51e96c0c5542b70659e17b;hb=HEAD>

-- 
VH

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References:
- Fwd: [PATCH] spinlock spin with pause instruction
  - From: VÃclav Haisman
- Re: Fwd: [PATCH] spinlock spin with pause instruction
  - From: Mark Geisert

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