Subject: Re: splx() optimization [was Re: SMP re-eetrancy in "bottom half" drivers]
To: Jonathan Stone <jonathan@dsg.stanford.edu>
From: Jason Thorpe <thorpej@shagadelic.org>
List: tech-kern
Date: 06/10/2005 16:19:14
On Jun 10, 2005, at 4:06 PM, Jonathan Stone wrote:

> But it's far from clear whether this will help or hurt.
>
> Look, here you're basically proposing trading a synchronization op (at
> whatever hypothetical granularity we need synchronization), for a
> memory barrier.  There are microarchitectures (CPU pipelines, if you
> will) where atomic memory-op acts on a single cacheline and doesn't
> imply any memory barriers. If your pipeline is also OOO, memory
> barriers could be _way_ more expensive.

Right, that was basically my point.

-- thorpej