Re: [boost] [thread] semaphore

Subject: Re: [boost] [thread] semaphore
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2013-09-21 17:30:12

On 20 Sep 2013 at 20:02, Ion Gaztañaga wrote:

> Should we have different "optimized" versions of a semaphore depending 
> on the memory order guarantees? I'd love to hear what memory-model 
> experts think about this.

On Intel, it's very tough to debug relaxed memory order code as Intel 
does very litle reordering relative to other CPUs.

ARM is better, but I believe it needs an Alpha to really get the bugs 
out.

There is, surely, some magic tool for LLVM somewhere which will 
output all programs doing all possible reordering combinations for 
some bit of code. That would reveal bugs even on Intel.

BTW, I'd suspect you'll gain far more performance from sync 
primitives written using TM than from relaxed memory ordering. If 
you're going to expend effort there, far better to do so on TM 
implementations despite the lack of TM capable hardware.

Niall

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