From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751738AbXCXBkf (ORCPT ); Fri, 23 Mar 2007 21:40:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751809AbXCXBkf (ORCPT ); Fri, 23 Mar 2007 21:40:35 -0400 Received: from kanga.kvack.org ([66.96.29.28]:39088 "EHLO kanga.kvack.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751738AbXCXBke (ORCPT ); Fri, 23 Mar 2007 21:40:34 -0400 Date: Fri, 23 Mar 2007 21:40:24 -0400 From: Benjamin LaHaise To: Christoph Hellwig , Ken Chen , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [patch] cache pipe buf page address for non-highmem arch Message-ID: <20070324014024.GL17334@kvack.org> References: <20070323101452.GA15144@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070323101452.GA15144@infradead.org> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 23, 2007 at 10:14:52AM +0000, Christoph Hellwig wrote: > I think you're fixing the symptom here and not the cause. If calculating > the virtual address of a page is so expensive on your setup it should > define WANT_PAGE_VIRTUAL and we should always cache the virtual address > in struct page. There's a lot more code, epecially in filesystems that's > rather upset about a slow page_address. Andi shot that down when I brought it up a while ago, as it does show up in profiles for networking and other code paths. His argument is that the loss of memory is excessive. Personally, I think the benefits of a 64 byte struct page on x86-64 outweigh the memory loss, as it means page index to address translations are a simple shift. -ben -- "Time is of no importance, Mr. President, only life is important." Don't Email: .