From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Fri, 25 Mar 2005 19:37:49 +0000 (GMT) Received: from nevyn.them.org ([IPv6:::ffff:66.93.172.17]:58598 "EHLO nevyn.them.org") by linux-mips.org with ESMTP id ; Fri, 25 Mar 2005 19:37:27 +0000 Received: from drow by nevyn.them.org with local (Exim 4.50 #1 (Debian)) id 1DEud5-00060b-Rl; Fri, 25 Mar 2005 14:37:59 -0500 Date: Fri, 25 Mar 2005 14:37:59 -0500 From: Daniel Jacobowitz To: Ed Martini Cc: linux-mips@linux-mips.org Subject: Re: Observations on LLSC and SMP Message-ID: <20050325193759.GA23046@nevyn.them.org> References: <4230DB4C.7090103@c2micro.com> <20050314110101.GF7759@linux-mips.org> <423763B9.2000907@c2micro.com> <20050316120647.GB8563@linux-mips.org> <42446555.6090005@c2micro.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <42446555.6090005@c2micro.com> User-Agent: Mutt/1.5.6+20040907i Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 7525 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: dan@debian.org Precedence: bulk X-list: linux-mips On Fri, Mar 25, 2005 at 11:24:05AM -0800, Ed Martini wrote: > 1. If the first part of the if were an ifdef instead it would result in > a code size reduction as well as a runtime performance gain. You should spend a little time playing with an optimizing compiler. They're capable of working out when a condition will always be false. > 2. In atomic.h the "C lang stuff" is wrapped with a spinlock. In the > SMP case the spinlock will result in code that contains ll and sc > instructions, so I infer that there are no SMP system configs that use > CPUs that don't have the ll and sc instructions. That's correct. It is not practical to implement SMP without a mutex primitive. -- Daniel Jacobowitz CodeSourcery, LLC