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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 0EE2DC4320E for ; Mon, 30 Aug 2021 13:49:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E53D260C3F for ; Mon, 30 Aug 2021 13:49:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236918AbhH3NuR (ORCPT ); Mon, 30 Aug 2021 09:50:17 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:47326 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231669AbhH3NuP (ORCPT ); Mon, 30 Aug 2021 09:50:15 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id BE0CC200AB; Mon, 30 Aug 2021 13:49:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1630331360; 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=cc2jyFkI4Y/eTP0fuxxH8ESHEZFe6V2z4lrRtmnXM6Q=; b=f9o3YxtNcrKp+PK+ZWm2qAcsw5SLHc0jhEZNVj2f5bET7VWTGz50zzq8TpyCC/RXE458Tf lSeFAgCdD9JtLnXb3jnosfjBDxBo6eXU50D46GUyB+DEzAz3eANVJR3QcOCnV1V7yPUKAJ xoHh8NZSrT3v+aSLPdXND61QpTGNN4g= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 94E53A3B9F; Mon, 30 Aug 2021 13:49:19 +0000 (UTC) Date: Mon, 30 Aug 2021 15:49:19 +0200 From: Michal Hocko To: yong w Cc: Tejun Heo , Jonathan Corbet , Andrew Morton , Vladimir Davydov , Thomas Gleixner , "Peter Zijlstra (Intel)" , Shakeel Butt , Roman Gushchin , alexs@kernel.org, Wei Yang , Hui Su , Stephen Rothwell , wang.yong12@zte.com.cn, Cgroups , linux-doc@vger.kernel.org, LKML , Linux MM , yang.yang29@zte.com.cn Subject: Re: [PATCH v2] mm: Add configuration to control whether vmpressure notifier is enabled Message-ID: References: <1629417219-74853-1-git-send-email-wang.yong12@zte.com.cn> 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 Sun 22-08-21 17:46:08, yong w wrote: > > All those reasons should be a part of the changelog. > >.... > > I am not sure these are sufficient justifications but that is something > > to discuss. And hence it should be a part of the changelog. > > > OK, These reasons will be added to the patch notesin later versions. > > > > 3. In the case where the user does not need vmpressure, vmpressure > > > calculation is additional overhead. > > > > You should quantify that and argue why that overhead cannot be further > > reduced without config/boot time knobs. > > > The test results of the previously used PFT tool may not be obvious. > Is there a better way to quantify it? This is a question for you to answer I am afraid. You want to add a configuration option and (as explained) that is not free of cost from the maintenance POV. There must a very good reason to do that. > > > In some special scenes with tight memory, vmpressure will be executed > > > frequently.we use "likely" and "inline" > > > to improve the performance of the kernel, why not reduce some > > > unnecessary calculations? > > > > I am all for improving the code. Is it possible to do it by other means? > > E.g. reduce a potential overhead when there no events registered? > Yes, the method you mentioned may be feasible, but it does not conflict > with this patch. It is not in conflict but runtime overhead reduction without more burden on the configurability is usually a preferred approach. -- Michal Hocko SUSE Labs