From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 648542114A6A2 for ; Tue, 25 Sep 2018 15:14:22 -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> <8faf3acc-e47e-8ef9-a1a0-c0d6ebfafa1e@linux.intel.com> From: Dave Hansen Message-ID: <75dde720-c997-51a4-d2e2-8b08eb201550@intel.com> Date: Tue, 25 Sep 2018 15:14:21 -0700 MIME-Version: 1.0 In-Reply-To: <8faf3acc-e47e-8ef9-a1a0-c0d6ebfafa1e@linux.intel.com> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Alexander Duyck , 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, jglisse@redhat.com, rppt@linux.vnet.ibm.com, mingo@kernel.org, kirill.shutemov@linux.intel.com List-ID: T24gMDkvMjUvMjAxOCAwMTozOCBQTSwgQWxleGFuZGVyIER1eWNrIHdyb3RlOgo+IE9uIDkvMjUv MjAxOCAxOjI2IFBNLCBEYXZlIEhhbnNlbiB3cm90ZToKPj4gT24gMDkvMjUvMjAxOCAwMToyMCBQ TSwgQWxleGFuZGVyIER1eWNrIHdyb3RlOgo+Pj4gK8KgwqDCoCB2bV9kZWJ1Z1s9b3B0aW9uc13C oMKgwqAgW0tOTF0gQXZhaWxhYmxlIHdpdGggQ09ORklHX0RFQlVHX1ZNPXkuCj4+PiArwqDCoMKg wqDCoMKgwqDCoMKgwqDCoCBNYXkgc2xvdyBkb3duIHN5c3RlbSBib290IHNwZWVkLCBlc3BlY2lh bGx5IHdoZW4KPj4+ICvCoMKgwqDCoMKgwqDCoMKgwqDCoMKgIGVuYWJsZWQgb24gc3lzdGVtcyB3 aXRoIGEgbGFyZ2UgYW1vdW50IG9mIG1lbW9yeS4KPj4+ICvCoMKgwqDCoMKgwqDCoMKgwqDCoMKg IEFsbCBvcHRpb25zIGFyZSBlbmFibGVkIGJ5IGRlZmF1bHQsIGFuZCB0aGlzCj4+PiArwqDCoMKg 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c3RzLjAxLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2xpbnV4LW52ZGltbQo= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) by kanga.kvack.org (Postfix) with ESMTP id 51CD18E00A4 for ; Tue, 25 Sep 2018 18:14:23 -0400 (EDT) Received: by mail-pg1-f198.google.com with SMTP id s7-v6so3749829pgp.3 for ; Tue, 25 Sep 2018 15:14:23 -0700 (PDT) Received: from mga01.intel.com (mga01.intel.com. [192.55.52.88]) by mx.google.com with ESMTPS id d5-v6si3535366pla.439.2018.09.25.15.14.21 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Sep 2018 15:14:22 -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> <8faf3acc-e47e-8ef9-a1a0-c0d6ebfafa1e@linux.intel.com> From: Dave Hansen Message-ID: <75dde720-c997-51a4-d2e2-8b08eb201550@intel.com> Date: Tue, 25 Sep 2018 15:14:21 -0700 MIME-Version: 1.0 In-Reply-To: <8faf3acc-e47e-8ef9-a1a0-c0d6ebfafa1e@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Alexander Duyck , 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 09/25/2018 01:38 PM, Alexander Duyck wrote: > On 9/25/2018 1:26 PM, Dave Hansen wrote: >> On 09/25/2018 01:20 PM, Alexander Duyck wrote: >>> +A A A vm_debug[=options]A A A [KNL] Available with CONFIG_DEBUG_VM=y. >>> +A A A A A A A A A A A May slow down system boot speed, especially when >>> +A A A A A A A A A A A enabled on systems with a large amount of memory. >>> +A A A A A A A A A A A All options are enabled by default, and this >>> +A A A A A A A A A A A interface is meant to allow for selectively >>> +A A A A A A A A A A A enabling or disabling specific virtual memory >>> +A A A A A A A A A A A debugging features. >>> + >>> +A A A A A A A A A A A Available options are: >>> +A A A A A A A A A A A A A PA A A Enable page structure init time poisoning >>> +A A A A A A A A A A A A A -A A A Disable all of the above options >> >> Can we have vm_debug=off for turning things off, please?A 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. We don't have to have the same letters mean the same things for both options. We also can live without 'o' and 'f' being valid. We can *also* just say "don't do 'off'" if you want to enable things. I'd much rather have vm_debug=off do the right thing than have per-feature enable/disable. I know I'll *never* remember vm_debug=- and doing it this way will subject me to innumerable trips to Documentation/ during my few remaining years. Surely you can make vm_debug=off happen. :) >> we need to document the defaults.A 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, an> this interface is meant to allow for selectively enabling or disabling". I found "all options are enabled by default" really confusing. Maybe: "Control debug features which become available when CONFIG_DEBUG_VM=y. When this option is not specified, all debug features are enabled. Use this option enable a specific subset." Then, let's actually say what the options do, and what their impact is: P Enable 'struct page' poisoning at initialization. (Slows down boot time). 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 69EA1C43382 for ; Tue, 25 Sep 2018 22:14:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0BA762086E for ; Tue, 25 Sep 2018 22:14:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0BA762086E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=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 S1726175AbeIZEYC (ORCPT ); Wed, 26 Sep 2018 00:24:02 -0400 Received: from mga18.intel.com ([134.134.136.126]:20948 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725736AbeIZEYC (ORCPT ); Wed, 26 Sep 2018 00:24:02 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Sep 2018 15:14:21 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,303,1534834800"; d="scan'208";a="76174267" Received: from vdevara1-mobl.amr.corp.intel.com (HELO [10.251.19.174]) ([10.251.19.174]) by orsmga008.jf.intel.com with ESMTP; 25 Sep 2018 15:14:21 -0700 Subject: Re: [PATCH v5 2/4] mm: Provide kernel parameter to allow disabling page init poisoning To: Alexander Duyck , linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org References: <20180925200551.3576.18755.stgit@localhost.localdomain> <20180925201921.3576.84239.stgit@localhost.localdomain> <13285e05-fb90-b948-6f96-777f94079657@intel.com> <8faf3acc-e47e-8ef9-a1a0-c0d6ebfafa1e@linux.intel.com> 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 From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <8faf3acc-e47e-8ef9-a1a0-c0d6ebfafa1e@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/25/2018 01:38 PM, Alexander Duyck wrote: > 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. We don't have to have the same letters mean the same things for both options. We also can live without 'o' and 'f' being valid. We can *also* just say "don't do 'off'" if you want to enable things. I'd much rather have vm_debug=off do the right thing than have per-feature enable/disable. I know I'll *never* remember vm_debug=- and doing it this way will subject me to innumerable trips to Documentation/ during my few remaining years. Surely you can make vm_debug=off happen. :) >> 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, an> this interface is meant to allow for selectively enabling or disabling". I found "all options are enabled by default" really confusing. Maybe: "Control debug features which become available when CONFIG_DEBUG_VM=y. When this option is not specified, all debug features are enabled. Use this option enable a specific subset." Then, let's actually say what the options do, and what their impact is: P Enable 'struct page' poisoning at initialization. (Slows down boot time).