Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764930AbXH0Vvx (ORCPT ); Mon, 27 Aug 2007 17:51:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932575AbXH0Vit (ORCPT ); Mon, 27 Aug 2007 17:38:49 -0400 Received: from tomts13-srv.bellnexxia.net ([209.226.175.34]:38135 "EHLO tomts13-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933429AbXH0Vir (ORCPT ); Mon, 27 Aug 2007 17:38:47 -0400 Date: Mon, 27 Aug 2007 17:38:45 -0400 From: Mathieu Desnoyers To: Christoph Lameter Cc: Peter Zijlstra , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, mingo@redhat.com Subject: Re: [PATCH] SLUB use cmpxchg_local Message-ID: <20070827213845.GB9748@Krystal> References: <20070821173849.GA8360@Krystal> <1188197539.6114.426.camel@twins> <20070827202203.GB5653@Krystal> <20070827203913.GA7416@Krystal> <20070827211003.GA10627@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 17:35:19 up 28 days, 21:54, 7 users, load average: 0.18, 0.24, 0.43 User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1650 Lines: 49 * Christoph Lameter (clameter@sgi.com) wrote: > On Mon, 27 Aug 2007, Mathieu Desnoyers wrote: > > > > a clean solution source code wise. It also minimizes the interrupt holdoff > > > for the non-cmpxchg_local arches. However, it means that we will have to > > > disable interrupts twice for the slow path. If that is too expensive then > > > we need a different solution. > > > > > > > cmpxchg_local is not used on the slow path... ? > > Right. > > > Did you meant: > > > > it means that we will have to disable preemption _and_ interrupts on the > > fast path for non-cmpxchg_local arches ? > > We would have to disable preemption and interrupts once on the fast path. > The interrupt holdoff would just be a couple of instructions. > Right. > The slow path would require disable preemption and two interrupt disables. > If the slow path have to call new_slab, then yes. But it seems that not every slow path must call it, so for the other slow paths, only one interrupt disable would be required. > Question is if this makes sense performance wise. If not then we may have > to look at more complicated schemes. > Yep, such as the arch_have_cmpxchg() macro that I proposed, but it really hurts my eyes... :( Mathieu -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - 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/