From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH] Get rid of zone_table V2 Date: Tue, 19 Sep 2006 20:24:54 +0200 References: <45101EAE.2070303@yahoo.com.au> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200609192024.54477.ak@suse.de> Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Nick Piggin , Andrew Morton , linux-mm@kvack.org, Andy Whitcroft , Dave Hansen List-ID: On Tuesday 19 September 2006 19:50, Christoph Lameter wrote: > On Wed, 20 Sep 2006, Nick Piggin wrote: > > > BTW. I wonder why gcc isn't using two shifts in your example? Not that > > I think it would be great even if it were, because subtle differences > > could cause that to become more shifts... > > Perhaps multiply is highly optimized in contemporary processors and I am > worrying too much about the multiply? It is. e.g. an Opteron can do a multiply in 3-4 cycles Just arbitary division is still slow. Division by constant is usually also not that bad because the compiler can decompose it into multiplies and other operations. -Andi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org