From mboxrd@z Thu Jan 1 00:00:00 1970 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 82C1CCDB482 for ; Thu, 12 Oct 2023 12:50:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378427AbjJLMuF (ORCPT ); Thu, 12 Oct 2023 08:50:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43324 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343872AbjJLMuE (ORCPT ); Thu, 12 Oct 2023 08:50:04 -0400 Received: from outbound-smtp56.blacknight.com (outbound-smtp56.blacknight.com [46.22.136.240]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 33BBC91 for ; Thu, 12 Oct 2023 05:50:02 -0700 (PDT) Received: from mail.blacknight.com (pemlinmail05.blacknight.ie [81.17.254.26]) by outbound-smtp56.blacknight.com (Postfix) with ESMTPS id 8BB39FB099 for ; Thu, 12 Oct 2023 13:50:00 +0100 (IST) Received: (qmail 5189 invoked from network); 12 Oct 2023 12:50:00 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.197.19]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 12 Oct 2023 12:50:00 -0000 Date: Thu, 12 Oct 2023 13:49:58 +0100 From: Mel Gorman To: "Huang, Ying" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Arjan Van De Ven , Andrew Morton , Vlastimil Babka , David Hildenbrand , Johannes Weiner , Dave Hansen , Michal Hocko , Pavel Tatashin , Matthew Wilcox , Christoph Lameter Subject: Re: [PATCH 09/10] mm, pcp: avoid to reduce PCP high unnecessarily Message-ID: <20231012124958.dj5ug5hih3joa542@techsingularity.net> References: <20230920061856.257597-1-ying.huang@intel.com> <20230920061856.257597-10-ying.huang@intel.com> <20231011140949.rwsqfb57vyuub6va@techsingularity.net> <87lec8ffij.fsf@yhuang6-desk2.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <87lec8ffij.fsf@yhuang6-desk2.ccr.corp.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 12, 2023 at 03:48:04PM +0800, Huang, Ying wrote: > " > On a 2-socket Intel server with 224 logical CPU, we run 8 kbuild > instances in parallel (each with `make -j 28`) in 8 cgroup. This > simulates the kbuild server that is used by 0-Day kbuild service. > With the patch, The number of pages allocated from zone (instead of > from PCP) decreases 21.4%. > " > > I also showed the performance number for each step of optimization as > follows (copied from the above patchset V2 link). > > " > build time lock contend% free_high alloc_zone > ---------- ---------- --------- ---------- > base 100.0 13.5 100.0 100.0 > patch1 99.2 10.6 19.2 95.6 > patch3 99.2 11.7 7.1 95.6 > patch5 98.4 10.0 8.2 97.1 > patch7 94.9 0.7 3.0 19.0 > patch9 94.9 0.6 2.7 15.0 <-- this patch > patch10 94.9 0.9 8.8 18.6 > " > > Although I think the patch is helpful via avoiding the unnecessary > pcp->high decaying, thus reducing the zone lock contention. There's no > visible benchmark score change for the patch. > Thanks! Given that it's another PCP field with an update in a relatively hot path, I would suggest dropping this patch entirely if it does not affect performance. It has the risk of being a magical heuristic that we forget later whether it's even worthwhile. -- Mel Gorman SUSE Labs