Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763665AbZD3PD4 (ORCPT ); Thu, 30 Apr 2009 11:03:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762803AbZD3PDp (ORCPT ); Thu, 30 Apr 2009 11:03:45 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:60627 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762696AbZD3PDm (ORCPT ); Thu, 30 Apr 2009 11:03:42 -0400 Date: Thu, 30 Apr 2009 17:01:42 +0200 From: Ingo Molnar To: Christoph Lameter Cc: Mathieu Desnoyers , Linus Torvalds , Andrew Morton , Nick Piggin , KOSAKI Motohiro , Peter Zijlstra , thomas.pi@arcor.dea, Yuriy Lalym , Linux Kernel Mailing List , ltt-dev@lists.casi.polymtl.ca, Tejun Heo Subject: Re: [PATCH] Fix dirty page accounting in redirty_page_for_writepage() Message-ID: <20090430150142.GC20580@elte.hu> References: <20090429232546.GB15782@Krystal> <20090430024303.GB19875@Krystal> <20090430133859.GB8329@elte.hu> <20090430141446.GD14696@elte.hu> <20090430143819.GF14696@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1350 Lines: 34 * Christoph Lameter wrote: > On Thu, 30 Apr 2009, Ingo Molnar wrote: > > > > Yes but sometimes you are already irq safe and such a fallback > > > would create significant irq/enable/disable stack operations etc > > > overhead for architectures that are using the fallback. > > > > It's a fallback slowpath - non-x86 architectures should still fill > > in a real implementation of course. > > Arch code cannot provide an effective implementation since they > always have to assume that interupts need to be disabled if we stay with > the current implementation. > > > So we first have to see the list of architectures that _cannot_ > > implement an irq-safe op here via a single machine instruction. > > x86, ia64 and powerpc should be fine. > > Look at Ia64, sparc, s/390, powerpc. They can fall back to atomic > ops but those are very ineffective on some of these platforms. > Since these are performance critical they will need to be > optimized depending on the context of their use in the core. Could you cite a specific example / situation where you'd use __xxx ops? Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/