From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754260Ab1GGS4I (ORCPT ); Thu, 7 Jul 2011 14:56:08 -0400 Received: from waste.org ([173.11.57.241]:51376 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752798Ab1GGS4D (ORCPT ); Thu, 7 Jul 2011 14:56:03 -0400 Subject: Re: [PATCH] slub: reduce overhead of slub_debug From: Matt Mackall To: Pekka Enberg Cc: Christoph Lameter , Marcin Slusarz , LKML , rientjes@google.com, linux-mm@kvack.org In-Reply-To: <1310064771.21902.55.camel@jaguar> References: <20110626193918.GA3339@joi.lan> <1310064771.21902.55.camel@jaguar> Content-Type: text/plain; charset="UTF-8" Date: Thu, 07 Jul 2011 13:55:59 -0500 Message-ID: <1310064959.3637.12.camel@calx> Mime-Version: 1.0 X-Mailer: Evolution 2.32.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2011-07-07 at 21:52 +0300, Pekka Enberg wrote: > On Thu, 7 Jul 2011, Pekka Enberg wrote: > > > Looks good to me. Christoph, David, ? > > On Thu, 2011-07-07 at 13:17 -0500, Christoph Lameter wrote: > > The reason debug code is there is because it is useless overhead typically > > not needed. There is no point in optimizing the code that is not run in > > production environments unless there are gross performance issues that > > make debugging difficult. A performance patch for debugging would have to > > cause significant performance improvements. This patch does not do that > > nor was there such an issue to be addressed in the first place. > > Is there something technically wrong with the patch? Quoting the patch > email: > > (Compiling some project with different options) > make -j12 make clean > slub_debug disabled: 1m 27s 1.2 s > slub_debug enabled: 1m 46s 7.6 s > slub_debug enabled + this patch: 1m 33s 3.2 s > > check_bytes still shows up high, but not always at the top. > > That's significant enough speedup for me! We're not going to make any progress on this; Christoph conveniently forgets the counterarguments from week to week. -- Mathematics is the supreme nostalgia of our time.