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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 C7D9DC31E40 for ; Tue, 6 Aug 2019 11:11:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9FA4C20B1F for ; Tue, 6 Aug 2019 11:11:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565089874; bh=TMm6oqmx5PpUGjqqMqLwT0Tqw0Nq4KsVh/fjsfwMlJc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=WOW0B1pQM7QO/RQMYMhQfJuyhapslk+O4QNa9sGotJgnPI5BRK+iX5yRYtepmbucG aTUjkSYeSwV772kCGaVQCmwNtsWNiQwnnqft0TojrxbYnvgnQ0Ic8mg7GaOw7/3JMY R5A37q4iZW8doL10UBbsJCmmztmym0/S/71EffIg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731235AbfHFLLN (ORCPT ); Tue, 6 Aug 2019 07:11:13 -0400 Received: from mx2.suse.de ([195.135.220.15]:48218 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728845AbfHFLLN (ORCPT ); Tue, 6 Aug 2019 07:11:13 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id DB69CB629; Tue, 6 Aug 2019 11:11:11 +0000 (UTC) Date: Tue, 6 Aug 2019 13:11:09 +0200 From: Michal Hocko To: Minchan Kim Cc: kernel test robot , Andrew Morton , LKML , linux-mm , Miguel de Dios , Wei Wang , Johannes Weiner , Mel Gorman , lkp@01.org Subject: Re: [mm] 755d6edc1a: will-it-scale.per_process_ops -4.1% regression Message-ID: <20190806111109.GV11812@dhcp22.suse.cz> References: <20190729071037.241581-1-minchan@kernel.org> <20190806070547.GA10123@xsang-OptiPlex-9020> <20190806080415.GG11812@dhcp22.suse.cz> <20190806110024.GA32615@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190806110024.GA32615@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 06-08-19 20:00:24, Minchan Kim wrote: > On Tue, Aug 06, 2019 at 10:04:15AM +0200, Michal Hocko wrote: > > On Tue 06-08-19 15:05:47, kernel test robot wrote: > > > Greeting, > > > > > > FYI, we noticed a -4.1% regression of will-it-scale.per_process_ops due to commit: > > > > I have to confess I cannot make much sense from numbers because they > > seem to be too volatile and the main contributor doesn't stand up for > > me. Anyway, regressions on microbenchmarks like this are not all that > > surprising when a locking is slightly changed and the critical section > > made shorter. I have seen that in the past already. > > I guess if it's multi process workload. The patch will give more chance > to be scheduled out so TLB miss ratio would be bigger than old. > I see it's natural trade-off for latency vs. performance so only thing > I could think is just increase threshold from 32 to 64 or 128? This still feels like a magic number tunning, doesn't it? -- Michal Hocko SUSE Labs