Re: [Boost-build] x86 CPU spinning should use pause

Subject: Re: [Boost-build] x86 CPU spinning should use pause
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2011-09-28 13:12:25

On Wed, 28 Sep 2011, Hite, Christopher wrote:

> #define BOOST_SMT_PAUSE __asm__ __volatile__( "rep; nop" : : : "memory" );
>  
> We should probably use:
>         __asm__ __volatile__("pause;")
>  
> Why? Because one thread polling( or worse CASing) memory, causes multiple overlapping memory operations to be made:

See 
http://stackoverflow.com/questions/7086220/what-does-rep-nop-mean-in-x86-assembly 
-- basically, "rep; nop" is exactly the same instruction as "pause".

-- Jeremiah Willcock