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 X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68B57C433DF for ; Wed, 26 Aug 2020 01:46:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3D79C206E3 for ; Wed, 26 Aug 2020 01:46:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726700AbgHZBqC (ORCPT ); Tue, 25 Aug 2020 21:46:02 -0400 Received: from mga03.intel.com ([134.134.136.65]:48706 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726599AbgHZBqB (ORCPT ); Tue, 25 Aug 2020 21:46:01 -0400 IronPort-SDR: I+KjmFhqnqChobdF0J/4eLyiKgLlO/4Mt9vIrIJYoFZzDTWi4z6vpIGI8IR1EwCFDxeQpjTHib RIYUMTbut+Zw== X-IronPort-AV: E=McAfee;i="6000,8403,9724"; a="156211434" X-IronPort-AV: E=Sophos;i="5.76,354,1592895600"; d="scan'208";a="156211434" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2020 18:46:01 -0700 IronPort-SDR: bywuvKU1786MClS10ZZLwShMJM+68apVAuEAph5z9aduHixWIjk4bwKZsdL4ObFh2DQWOYYOyQ YKQBgTLOQg2Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.76,354,1592895600"; d="scan'208";a="336692138" Received: from shbuild999.sh.intel.com (HELO localhost) ([10.239.146.107]) by FMSMGA003.fm.intel.com with ESMTP; 25 Aug 2020 18:45:59 -0700 Date: Wed, 26 Aug 2020 09:45:58 +0800 From: Feng Tang To: "Luck, Tony" Cc: Borislav Petkov , "Chen, Rong A" , LKML , "lkp@lists.01.org" , Mel Gorman Subject: Re: [LKP] Re: [x86/mce] 1de08dccd3: will-it-scale.per_process_ops -14.1% regression Message-ID: <20200826014558.GC83850@shbuild999.sh.intel.com> References: <20200425130136.GA28245@zn.tnic> <20200818082943.GA65567@shbuild999.sh.intel.com> <20200818200654.GA21494@agluck-desk2.amr.corp.intel.com> <20200819020437.GA2605@shbuild999.sh.intel.com> <20200821020259.GA90000@shbuild999.sh.intel.com> <20200824151425.GF4794@zn.tnic> <20200824153300.GA56944@shbuild999.sh.intel.com> <20200824161238.GI4794@zn.tnic> <20200825062305.GA83850@shbuild999.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 26, 2020 at 12:44:37AM +0800, Luck, Tony wrote: > > These 2 variables are accessed in 2 hot call stacks (for this 288 CPU > > Xeon Phi platform): > > This might be the key element of "weirdness" for this system. It > has 288 CPUs ... cache alignment problems are often not too bad > on "small" systems. The as you scale up to bigger machines you > suddenly hit some critical point and performance drops dramatically. > > It's good that you are picking up tips on how to bisect these and diagnose > the underlying problem. Number of cores is going to keep increasing, so > we will keep finding new issues like this. Yes, now we have one more bullet for shooting this kind of strange performance changes :) Thanks, Feng > -Tony