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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 9F733C43382 for ; Wed, 26 Sep 2018 16:19:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 49FD021527 for ; Wed, 26 Sep 2018 16:19:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 49FD021527 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.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 S1728510AbeIZWct (ORCPT ); Wed, 26 Sep 2018 18:32:49 -0400 Received: from mga18.intel.com ([134.134.136.126]:26260 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727285AbeIZWct (ORCPT ); Wed, 26 Sep 2018 18:32:49 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Sep 2018 09:19:07 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,306,1534834800"; d="scan'208";a="76115327" Received: from ahduyck-mobl.amr.corp.intel.com (HELO [10.7.198.154]) ([10.7.198.154]) by orsmga007.jf.intel.com with ESMTP; 26 Sep 2018 09:18:16 -0700 Subject: Re: [PATCH v5 2/4] mm: Provide kernel parameter to allow disabling page init poisoning To: Dave Hansen , Michal Hocko Cc: linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, pavel.tatashin@microsoft.com, dave.jiang@intel.com, jglisse@redhat.com, rppt@linux.vnet.ibm.com, dan.j.williams@intel.com, logang@deltatee.com, mingo@kernel.org, kirill.shutemov@linux.intel.com References: <20180925200551.3576.18755.stgit@localhost.localdomain> <20180925201921.3576.84239.stgit@localhost.localdomain> <20180926073831.GC6278@dhcp22.suse.cz> <98411844-19b7-a75b-d52c-6e2c46b40d57@intel.com> From: Alexander Duyck Message-ID: <0845f5c1-5737-3749-69dd-e7fb5d1b75c6@linux.intel.com> Date: Wed, 26 Sep 2018 09:18:16 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <98411844-19b7-a75b-d52c-6e2c46b40d57@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/26/2018 8:41 AM, Dave Hansen wrote: > On 09/26/2018 08:24 AM, Alexander Duyck wrote: >> With no options it works just like slub_debug and enables all >> available options. So in our case it is a NOP since we wanted the >> debugging enabled by default. > > Yeah, but slub_debug is different. > > First, nobody uses the slub_debug=- option because *that* is only used > when you have SLUB_DEBUG=y *and* CONFIG_SLUB_DEBUG_ON=y, which not even > Fedora does. > > slub_debug is *primarily* for *adding* debug features. For this, we > need to turn them off. > > It sounds like following slub_debug was a bad idea, especially following > its semantics too closely when it doesn't make sense. I actually like the idea of using slub_debug style semantics. It makes sense when you start thinking about future features being added. Then we might actually have scenarios where vm_debug=P will make sense, but for right now it is probably not going to be used. Basically this all makes room for future expansion. It is just ugly to read right now while we only have one feature controlled by this bit.