From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f197.google.com (mail-pf1-f197.google.com [209.85.210.197]) by kanga.kvack.org (Postfix) with ESMTP id 247E98E00A4 for ; Tue, 25 Sep 2018 16:49:09 -0400 (EDT) Received: by mail-pf1-f197.google.com with SMTP id x19-v6so13302831pfh.15 for ; Tue, 25 Sep 2018 13:49:09 -0700 (PDT) Received: from mga01.intel.com (mga01.intel.com. [192.55.52.88]) by mx.google.com with ESMTPS id q4-v6si3388817pgj.417.2018.09.25.13.49.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Sep 2018 13:49:07 -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> <13285e05-fb90-b948-6f96-777f94079657@intel.com> From: Alexander Duyck Message-ID: <8faf3acc-e47e-8ef9-a1a0-c0d6ebfafa1e@linux.intel.com> Date: Tue, 25 Sep 2018 13:38:43 -0700 MIME-Version: 1.0 In-Reply-To: <13285e05-fb90-b948-6f96-777f94079657@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 , linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org Cc: pavel.tatashin@microsoft.com, mhocko@suse.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 9/25/2018 1:26 PM, Dave Hansen wrote: > On 09/25/2018 01:20 PM, Alexander Duyck wrote: >> + vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y. >> + May slow down system boot speed, especially when >> + enabled on systems with a large amount of memory. >> + All options are enabled by default, and this >> + interface is meant to allow for selectively >> + enabling or disabling specific virtual memory >> + debugging features. >> + >> + Available options are: >> + P Enable page structure init time poisoning >> + - Disable all of the above options > > Can we have vm_debug=off for turning things off, please? That seems to > be pretty standard. No. The simple reason for that is that you had requested this work like the slub_debug. If we are going to do that then each individual letter represents a feature. That is why the "-" represents off. We cannot have letters represent flags, and letters put together into words. For example slub_debug=OFF would turn on sanity checks and turn off debugging for caches that would have causes higher minimum slab orders. Either I can do this as a single parameter that supports on/off semantics, or I can support it as a slub_debug type parameter that does flags based on the input options. I would rather not muddy things by trying to do both. > Also, we need to document the defaults. I think the default is "all > debug options are enabled", but it would be nice to document that. In the description I call out "All options are enabled by default, and this interface is meant to allow for selectively enabling or disabling".