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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 40581C43441 for ; Mon, 19 Nov 2018 08:09:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DE9DD20823 for ; Mon, 19 Nov 2018 08:09:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DE9DD20823 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726744AbeKSScP (ORCPT ); Mon, 19 Nov 2018 13:32:15 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:37602 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726348AbeKSScP (ORCPT ); Mon, 19 Nov 2018 13:32:15 -0500 Received: from p4fea46ac.dip0.t-ipconnect.de ([79.234.70.172] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1gOecO-0001Pu-Tu; Mon, 19 Nov 2018 09:09:17 +0100 Date: Mon, 19 Nov 2018 09:09:16 +0100 (CET) From: Thomas Gleixner To: Qian Cai cc: Andrew Morton , Waiman Long , Yang Shi , arnd@arndb.de, linux kernel Subject: Re: [PATCH] debugobjects: add a new Kconfig for POOL_SIZE In-Reply-To: <5939F7F3-E332-4112-861E-C6C0DF86717E@gmx.us> Message-ID: References: <20181118082255.1275-1-cai@gmx.us> <5939F7F3-E332-4112-861E-C6C0DF86717E@gmx.us> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Qian, On Sun, 18 Nov 2018, Qian Cai wrote: > > On Nov 18, 2018, at 1:21 PM, Thomas Gleixner wrote: > > On Sun, 18 Nov 2018, Qian Cai wrote: > >> As the results, systems have 60+ CPUs with both timer and workqueue > >> objects enabled could trigger "ODEBUG: Out of memory. ODEBUG disabled". > >> > >> Hence, add a new Kconfig option so users could adjust ODEBUG_POOL_SIZE > >> accordingly if either timer or workqueue objects are selected. > > > > why do we need a config option, when the required number can be deduced > > already from the active CONFIG_DEBUG_OBJECTS_* and NR_CPUS? > > > It because I am worry about the coupling between the implementation details of > timers and workqueue objects, and the computation in the code you mentioned > here. For example, people could change workqueue.c to have different number > of worekqueues initialized during the early boot in the future which is going to > affect the required pool size, and I am not sure if people are going to adjust the > code in debugobjects.c here as well when they made changes like that. > > Also, the computation could become so complex depends on lots of config > options like perf, hrtimer, and combinations that I have not tested so far which is > difficult to exhausted all the possibilities. > > Hence, I feel like the Kconfig option is more flexible and less error-prone. Quite the contrary. Config options are a pain and truly error-prone if you want to compile general purpose kernels as distributions do. Its not really a problem to have a larger initial static pool which gets freed after init anyway. So we can size it generously depending on the config options and be done with it. Thanks, tglx