From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Date: Fri, 31 Mar 2006 16:37:33 +0000 Subject: Re: Synchronizing Bit operations V2 Message-Id: <200603311837.34477.ak@suse.de> List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Hans Boehm Cc: Christoph Lameter , Zoltan Menyhart , "Grundler, Grant G" , "Chen, Kenneth W" , akpm@osdl.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org On Friday 31 March 2006 18:22, Hans Boehm wrote: > My impression is that approach (1) tends not to stick, since it involves > a substantial performance hit on architectures on which the fence is > not implicitly included in atomic operations. Those include Itanium and > PowerPC. At least the PPC people are eating the overhead because back when they didn't they had a long string of subtle powerpc only bugs caused by that It's a stability/maintainability vs performance issue. I doubt the performance advantage would be worth the additional work. I guess with the engineering time you would need to spend getting all this right you could do much more fruitful optimizations. -Andi