Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F12F4C05027 for ; Mon, 23 Jan 2023 08:58:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231480AbjAWI6e (ORCPT ); Mon, 23 Jan 2023 03:58:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44156 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230155AbjAWI6d (ORCPT ); Mon, 23 Jan 2023 03:58:33 -0500 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 54E7A14EA8 for ; Mon, 23 Jan 2023 00:58:32 -0800 (PST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id E6A9B1F388; Mon, 23 Jan 2023 08:58:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1674464310; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=gIYcLkIhHoIqMTHU7z0z+ani6y5ft7j45PE+7GKmbjU=; b=t56Gdt2YqfMDFP9ycCDdRfCDH0nRp9TEdZr+wahpxuHv9wvnt5U5uEP+aR5NfLD1ItMmGG NzRhTiJay4EawlaFHdnsWXwmjmjOeMDvptjwjENxtboarwYhULWQt3CQhuGojFUH5kBNw5 a9vFx/aDZNwt6NfUbkONweihqx8IENs= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id B97731357F; Mon, 23 Jan 2023 08:58:30 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id qRweLDZMzmMNZQAAMHmgww (envelope-from ); Mon, 23 Jan 2023 08:58:30 +0000 Date: Mon, 23 Jan 2023 09:58:30 +0100 From: Michal Hocko To: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Vlastimil Babka , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Ingo Molnar , Johannes Weiner , Shakeel Butt , Muchun Song , Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , Dennis Zhou , Tejun Heo Subject: Re: [PATCH mm-unstable] lib/Kconfig.debug: do not enable DEBUG_PREEMPT by default Message-ID: References: <20230121033942.350387-1-42.hyeyoo@gmail.com> <86e68d3b-b029-5e82-5bbc-e0ccc2ae1d36@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 21-01-23 20:54:15, Hyeonggon Yoo wrote: > On Sat, Jan 21, 2023 at 12:29:44PM +0100, Vlastimil Babka wrote: > > On 1/21/23 04:39, Hyeonggon Yoo wrote: > > > In workloads where this_cpu operations are frequently performed, > > > enabling DEBUG_PREEMPT may result in significant increase in > > > runtime overhead due to frequent invocation of > > > __this_cpu_preempt_check() function. > > > > > > This can be demonstrated through benchmarks such as hackbench where this > > > configuration results in a 10% reduction in performance, primarily due to > > > the added overhead within memcg charging path. > > > > > > Therefore, do not to enable DEBUG_PREEMPT by default and make users aware > > > of its potential impact on performance in some workloads. > > > > > > hackbench-process-sockets > > > debug_preempt no_debug_preempt > > > Amean 1 0.4743 ( 0.00%) 0.4295 * 9.45%* > > > Amean 4 1.4191 ( 0.00%) 1.2650 * 10.86%* > > > Amean 7 2.2677 ( 0.00%) 2.0094 * 11.39%* > > > Amean 12 3.6821 ( 0.00%) 3.2115 * 12.78%* > > > Amean 21 6.6752 ( 0.00%) 5.7956 * 13.18%* > > > Amean 30 9.6646 ( 0.00%) 8.5197 * 11.85%* > > > Amean 48 15.3363 ( 0.00%) 13.5559 * 11.61%* > > > Amean 79 24.8603 ( 0.00%) 22.0597 * 11.27%* > > > Amean 96 30.1240 ( 0.00%) 26.8073 * 11.01%* Do you happen to have any perf data collected during those runs? I would be interested in the memcg side of things. Maybe we can do something better there. -- Michal Hocko SUSE Labs