From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752106AbeERQaF (ORCPT ); Fri, 18 May 2018 12:30:05 -0400 Received: from mail-sn1nam02on0048.outbound.protection.outlook.com ([104.47.36.48]:18737 "EHLO NAM02-SN1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751450AbeERQaD (ORCPT ); Fri, 18 May 2018 12:30:03 -0400 From: Nadav Amit To: Borislav Petkov CC: Ingo Molnar , Peter Zijlstra , "linux-kernel@vger.kernel.org" , "x86@kernel.org" , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Josh Poimboeuf , Linus Torvalds , Andy Lutomirski , Peter Zijlstra , Denys Vlasenko Subject: Re: [PATCH 2/6] x86: bug: prevent gcc distortions Thread-Topic: [PATCH 2/6] x86: bug: prevent gcc distortions Thread-Index: AQHT7jbL50o+w3m6PkeKHm2HX6GyP6Q1H7KAgAAEMwCAACDIAIAAShCAgAASAACAAAGeAIAAAhWAgAAKDYA= Date: Fri, 18 May 2018 16:29:59 +0000 Message-ID: <2176DA84-C064-487F-A062-03A95884F15E@vmware.com> References: <20180517161402.78089-1-namit@vmware.com> <20180517161402.78089-3-namit@vmware.com> <20180518075853.GD12217@hirez.programming.kicks-ass.net> <20180518081354.GA11379@gmail.com> <20180518101114.GB17285@pd.tnic> <20180518154044.GE17285@pd.tnic> <30EDFE9B-CA25-42EE-A57F-E3054B84223E@vmware.com> <20180518155359.GF17285@pd.tnic> In-Reply-To: <20180518155359.GF17285@pd.tnic> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [208.91.2.2] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;SN2PR05MB2445;7:gGV9At6fR/UeBlP8Vqmok0ksc1wRoKeniOTuBWf7zUPKXwD49H2HL0Dy4Ted435OvZQ0n7MUpSMcOgLBz29FtMEuW+OYOOkQmgii9PzVgyBh/cDiDdGXMB5m3tg1TSuiWqZlnfEUwfM0LN6iVE4K9OFI+S6YviZxq/DT43GFQYv9LzYMoxBVUoeVQ8NTh3l9OvMXp2mcJcON+Qi6mOPs/V0pNMHu2u4N43ZZuUpCWhPvZQtbN1RpSgqCD/+UR6Ni;20:YMnrwoQtO1GZptyHaG4z08dWFM7+8UpEuzapdimdmsVHhFNGNQYqeIQNvNKyf3epD0BreRAcbcSekqz/hN+4YhwO7xiif0Hb9oU8nDLwbsVGhcyvAGHBxzo6sWdHGgI3sSyZIdQLWQW3+FBGiyhDbQeFgXiC5udkT2xnlXiY37s= x-ms-exchange-antispam-srfa-diagnostics: SOS; x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(5600026)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603328)(7153060)(7193020);SRVR:SN2PR05MB2445; x-ms-traffictypediagnostic: SN2PR05MB2445: x-microsoft-antispam-prvs: x-exchange-antispam-report-test: UriScan:; x-ms-exchange-senderadcheck: 1 x-exchange-antispam-report-cfa-test: BCL:0;PCL:0;RULEID:(8211001083)(6040522)(2401047)(5005006)(8121501046)(3002001)(93006095)(93001095)(3231254)(944501410)(52105095)(10201501046)(149027)(150027)(6041310)(20161123558120)(20161123560045)(20161123562045)(20161123564045)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(6072148)(201708071742011)(7699016);SRVR:SN2PR05MB2445;BCL:0;PCL:0;RULEID:;SRVR:SN2PR05MB2445; x-forefront-prvs: 0676F530A9 x-forefront-antispam-report: SFV:NSPM;SFS:(10009020)(396003)(366004)(39860400002)(39380400002)(346002)(376002)(199004)(189003)(102836004)(26005)(6506007)(14454004)(3280700002)(6346003)(7736002)(2900100001)(25786009)(82746002)(3660700001)(478600001)(33656002)(105586002)(5250100002)(5660300001)(229853002)(8676002)(81156014)(81166006)(6512007)(186003)(7416002)(2906002)(305945005)(6436002)(36756003)(76176011)(6486002)(8936002)(6246003)(53936002)(6116002)(83716003)(4326008)(6916009)(476003)(93886005)(316002)(11346002)(2616005)(3846002)(68736007)(66066001)(99286004)(446003)(106356001)(86362001)(486006)(97736004)(54906003);DIR:OUT;SFP:1101;SCL:1;SRVR:SN2PR05MB2445;H:SN2PR05MB2654.namprd05.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; authentication-results: spf=none (sender IP is ) smtp.mailfrom=namit@vmware.com; x-microsoft-antispam-message-info: uD3u9gzsLMFuISR/4bMpx/7RFqFfFctqFr5kNIFKQdW7zmMPTPhZ84+ssHQERS7PZ+SskkCXdHYPhFCgjBadjy8i/8GQWavPp1VvX5DvnsC86SH4eLahBHhTp2/uZuEAW4MUEE5oKntAibt8AbtL1PJ2BQhsnzpTCWu4GK2ondz5Wo3H3wpiDYleAXuP0vv4 spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="utf-8" Content-ID: MIME-Version: 1.0 X-MS-Office365-Filtering-Correlation-Id: 21d97d0a-8525-47af-2722-08d5bcdc9984 X-OriginatorOrg: vmware.com X-MS-Exchange-CrossTenant-Network-Message-Id: 21d97d0a-8525-47af-2722-08d5bcdc9984 X-MS-Exchange-CrossTenant-originalarrivaltime: 18 May 2018 16:29:59.5319 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b39138ca-3cee-4b4a-a4d6-cd83d9dd62f0 X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN2PR05MB2445 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id w4IGUBsh001027 Borislav Petkov wrote: > On Fri, May 18, 2018 at 03:46:33PM +0000, Nadav Amit wrote: >> In case you didn’t read the cover-letter: the patch-set does give a 2% >> performance improvement for #PF-MADV_DONTNEED microbenchmark loop. > > I saw it but *micro*-benchmark doesn't tell me a whole lot. If that > "improvement" is not visible in real workloads/benchmarks, then I'm just > as unimpressed. Funny. I found in my mailbox that you once wrote me: "It is a dumb idea, it doesn't bring us anything besides some superficial readability which you don't really need.” To the point, I think you exaggerate with the effect of the patch on the code readability: it is not much uglier than it was before, and the change is in a very specific point in the code.