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 C85A4C43441 for ; Mon, 19 Nov 2018 14:51:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 82EDA206BB for ; Mon, 19 Nov 2018 14:51:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 82EDA206BB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1729644AbeKTBPJ (ORCPT ); Mon, 19 Nov 2018 20:15:09 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51672 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729399AbeKTBPJ (ORCPT ); Mon, 19 Nov 2018 20:15:09 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3E60630832C7; Mon, 19 Nov 2018 14:51:18 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-55.bos.redhat.com [10.18.17.55]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6914F17F7A; Mon, 19 Nov 2018 14:51:17 +0000 (UTC) Subject: Re: [PATCH] debugobjects: add a new Kconfig for POOL_SIZE To: Qian Cai , Thomas Gleixner Cc: linux kernel , arnd@arndb.de, Andrew Morton , Yang Shi References: <20181118082255.1275-1-cai@gmx.us> <5939F7F3-E332-4112-861E-C6C0DF86717E@gmx.us> From: Waiman Long Openpgp: preference=signencrypt Autocrypt: addr=longman@redhat.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Mon, 19 Nov 2018 14:51:18 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/19/2018 08:27 AM, Qian Cai wrote: > On 11/19/18 at 3:09 AM, Thomas Gleixner wrote: > >> 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. >> > Ah, I never thought distributions people would > enable those debugging options. Distros like RHEL usually ship two kernels - one for production and one for debug. The debug kernel does have debugobjects enabled. Cheers, Longman