Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759132AbXHVADe (ORCPT ); Tue, 21 Aug 2007 20:03:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752734AbXHVADZ (ORCPT ); Tue, 21 Aug 2007 20:03:25 -0400 Received: from tomts43-srv.bellnexxia.net ([209.226.175.110]:35314 "EHLO tomts43-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752914AbXHVADZ (ORCPT ); Tue, 21 Aug 2007 20:03:25 -0400 Date: Tue, 21 Aug 2007 20:03:23 -0400 From: Mathieu Desnoyers To: Christoph Lameter Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, mingo@redhat.com Subject: Re: [PATCH] SLUB use cmpxchg_local Message-ID: <20070822000323.GG29691@Krystal> References: <20070820215413.GA28452@Krystal> <20070821173849.GA8360@Krystal> <20070821231216.GA29691@Krystal> <20070821233938.GD29691@Krystal> <20070821234702.GE29691@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: 19:57:15 up 23 days, 16 min, 3 users, load average: 0.81, 0.55, 0.42 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: 1805 Lines: 50 * Christoph Lameter (clameter@sgi.com) wrote: > On Tue, 21 Aug 2007, Mathieu Desnoyers wrote: > > > Are you running a UP or SMP kernel ? If you run a UP kernel, the > > cmpxchg_local and cmpxchg are identical. > > UP. > > > Oh, and if you run your tests at boot time, the alternatives code may > > have removed the lock prefix, therefore making cmpxchg and cmpxchg_local > > exactly the same. > > Tests were run at boot time. > > That still does not explain kmalloc not showing improvements. > Hrm, weird.. because it should. Here are the numbers I posted previously: The measurements I get (in cycles): enable interrupts (STI) disable interrupts (CLI) local CMPXCHG IA32 (P4) 112 82 26 x86_64 AMD64 125 102 19 So both AMD64 and IA32 should be improved. So why those improvements are not shown in your test ? A few possible causes: - Do you have any CONFIG_DEBUG_* options activated ? smp_processor_id() may end up being more expensive in these cases. - Rounding error.. you seem to round at 0.1ms, but I keep the values in cycles. The times that you get (1.1ms) seems strangely higher than mine, which are under 1000 cycles on a 3GHz system (less than 333ns). I guess there is both a ms - ns error there and/or not enough precision in your numbers. 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/