From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f200.google.com (mail-pg1-f200.google.com [209.85.215.200]) by kanga.kvack.org (Postfix) with ESMTP id ABF198E0001 for ; Wed, 26 Sep 2018 12:19:09 -0400 (EDT) Received: by mail-pg1-f200.google.com with SMTP id i189-v6so3259949pge.6 for ; Wed, 26 Sep 2018 09:19:09 -0700 (PDT) Received: from mga18.intel.com (mga18.intel.com. [134.134.136.126]) by mx.google.com with ESMTPS id d127-v6si5266593pfa.189.2018.09.26.09.19.08 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 26 Sep 2018 09:19:08 -0700 (PDT) Subject: Re: [PATCH v5 2/4] mm: Provide kernel parameter to allow disabling page init poisoning 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 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: owner-linux-mm@kvack.org List-ID: 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 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.