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=-17.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 CC8CCC433DB for ; Thu, 21 Jan 2021 19:02:31 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5516223A53 for ; Thu, 21 Jan 2021 19:02:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5516223A53 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B28B56B0006; Thu, 21 Jan 2021 14:02:30 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id AD9146B0007; Thu, 21 Jan 2021 14:02:30 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9A0CB6B0008; Thu, 21 Jan 2021 14:02:30 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0222.hostedemail.com [216.40.44.222]) by kanga.kvack.org (Postfix) with ESMTP id 829756B0006 for ; Thu, 21 Jan 2021 14:02:30 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 4175D6130 for ; Thu, 21 Jan 2021 19:02:30 +0000 (UTC) X-FDA: 77730703260.24.chin18_4c05ba127565 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin24.hostedemail.com (Postfix) with ESMTP id 15F321A4A0 for ; Thu, 21 Jan 2021 19:02:30 +0000 (UTC) X-HE-Tag: chin18_4c05ba127565 X-Filterd-Recvd-Size: 11610 Received: from aserp2130.oracle.com (aserp2130.oracle.com [141.146.126.79]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Thu, 21 Jan 2021 19:02:29 +0000 (UTC) Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 10LIwj6U014269; Thu, 21 Jan 2021 19:02:22 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : in-reply-to : content-type : content-transfer-encoding : mime-version; s=corp-2020-01-29; bh=QNBU65gmfBQoGvPM9Lfq7uOv7pwAPlni+8r4mg+Bwt0=; b=UhLkgXgiDMR9QL00NgS48zlS6RLJYrbp9JQMKiZ6rZ7vhaICBkh6fYA9FXRufOFRTznr yC2ETbmRIZxNeH325o61q5fesB/spR+nXmbaMAynBxjrakUSSMmtDu1THGt2+U08qa4F mYe34ex340UpJr/oDITkVZFdddlAqh4IxXVnSqn5FmmKxyQ1oSRndDd4RHlWfIVRpccX hsj/AByB0sLIHnu9IYAuQOTyfIi8CRy6wNM743Izz9OCzSoSoh+rPVqtsSt5w6PpOKp3 hQ4IbMcIigVzRxzQK1fe9As+vBNkjlTSRvZxSRRFuH6Xn6VsewJzuQbxOVsHIxKfYXz4 Qg== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by aserp2130.oracle.com with ESMTP id 3668qrgwaw-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 21 Jan 2021 19:02:22 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 10LItkjf193905; Thu, 21 Jan 2021 19:00:21 GMT Received: from nam12-mw2-obe.outbound.protection.outlook.com (mail-mw2nam12lp2043.outbound.protection.outlook.com [104.47.66.43]) by userp3030.oracle.com with ESMTP id 3668rfgajh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 21 Jan 2021 19:00:21 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=fg+FH92CdskNlT05E8jiZc2HDkDuwegkLD77OqbyKvlVeSqmn1zEJt3mAI8z51CdETx2j988/K8cRqm4cl2BXiL/YObnkcRmtVwxcm0W3JSsbTGdfTlj7Je5dUdkTDiX0EQhJod2ZBQV8avZc0js62z8Ih9cIyQFK9LN49LXUvjkf1+W/ZBxoQVz8vc3iOmlEjWvonfovFKjaxnj/hxkTTCft+QO9BD1oYbjstUlztlKjspzrTyKDbOcxso8Ks4NWAlmiPDhSu8VBwxGNxfNhRFL4Y34nuQ6FhOmON/NR2+5j4Aje34fBmGtCzbj9R3/RzRI9gi7K2Lt0FEThTihgg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=QNBU65gmfBQoGvPM9Lfq7uOv7pwAPlni+8r4mg+Bwt0=; b=GGm5VGss/+EaJ0DFLwth7Md34c1EzYd780iVESbi9HDq29DE+ONc14xKKE1PADvl9vKcBHKFY0a24KlqK4p1BDzFSz3mcZ41P7067297ZXO4FPcyTKsbPDJP8Qgc85HxmNOQjHKaW+sKA5lDewUgv0YbmeKjpFUAXkOdGM0l9OzRwiy2kWI1abXJ3CGtGqF0zWxP8klkrHsk/Jfdaja6kzWl6ow1L1pLkdLRPXKfuOXE0Gri28BwYyAvRv+bpigUzD8dcNXlBUxGVbqewFFp2zJ1fx1wZ/64f5iHiHhqedm4vQFe6tjpBXS+GIYVnHAd/Z9oXIwE6/xLV2bMhUzV2g== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=oracle.com; dmarc=pass action=none header.from=oracle.com; dkim=pass header.d=oracle.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.onmicrosoft.com; s=selector2-oracle-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=QNBU65gmfBQoGvPM9Lfq7uOv7pwAPlni+8r4mg+Bwt0=; b=Tq/ucDkVU+X9MCl0vtIuWXTIRAg4Vtbmcabya/kZbY9JDJVDy05h6K1vrRCMFyeRuLc+SdrMQrAC60v2R2a6nW3ngWNnnrLF8b++G03ImCLIxwZYotZ51uh3kbV/C1XqJQI4236T/nOx0BTDO+0R6cUswz+74PsS0F9qtWBTCOI= Authentication-Results: vger.kernel.org; dkim=none (message not signed) header.d=none;vger.kernel.org; dmarc=none action=none header.from=oracle.com; Received: from MWHPR10MB1389.namprd10.prod.outlook.com (2603:10b6:300:21::22) by MWHPR1001MB2112.namprd10.prod.outlook.com (2603:10b6:301:2e::24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3763.13; Thu, 21 Jan 2021 19:00:19 +0000 Received: from MWHPR10MB1389.namprd10.prod.outlook.com ([fe80::897d:a360:92db:3074]) by MWHPR10MB1389.namprd10.prod.outlook.com ([fe80::897d:a360:92db:3074%5]) with mapi id 15.20.3763.014; Thu, 21 Jan 2021 19:00:19 +0000 Subject: Re: [PATCH] hugetlbfs: make hugepage size conversion more readable To: Miaohe Lin , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210120092348.13811-1-linmiaohe@huawei.com> From: Mike Kravetz Message-ID: <668845df-e654-ecdc-c32a-b50a22098333@oracle.com> Date: Thu, 21 Jan 2021 11:00:16 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 In-Reply-To: <20210120092348.13811-1-linmiaohe@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [50.38.35.18] X-ClientProxiedBy: MW4PR04CA0214.namprd04.prod.outlook.com (2603:10b6:303:87::9) To MWHPR10MB1389.namprd10.prod.outlook.com (2603:10b6:300:21::22) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.2.112] (50.38.35.18) by MW4PR04CA0214.namprd04.prod.outlook.com (2603:10b6:303:87::9) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3784.11 via Frontend Transport; Thu, 21 Jan 2021 19:00:18 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 2c619f4e-d200-4dda-ba4f-08d8be3ecbd7 X-MS-TrafficTypeDiagnostic: MWHPR1001MB2112: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: o17mb5fD1XZuZHPiXP7piqizMHOd6PLT6c8w1QWkoe2SkFWTEZQBU+MlaJWlUdcGsYxxrlvt7dFjOcBOKVNLzJQGnFHEEzvBiMO6BqCrHHM6ejk9yhyq8pk1t7buXIi6Z2+UHam+sSCOplHbOn2pgzo/R9QrSVKA8aQrVjjWagZA1NYm9nb2B7u8BgWylYgWIalkrRQ/Z+1AudSsxRIByaollsMQyW4ANGxW6p+qYUw6WRJiRz9iwREw3JNoHa6yD4cDBXNrXOhlcmyhnppBH+rbFl6y8ysrf5CvS77cY3/adhCjajKWmZViIvf94XgjndCB2qEgwTZEy40S/Xj8VvcwtoMPEfNJqC61jWnQSGRSfEniKewvvYuf3nfV92kD291TtWhK7URtrFCd870QPPoPKJC28t9jsrISNUj76fghOpuhQ/WBBZ3fQEoxeLtP78qkO7f+y700ZGEudAhXaDegd0a9f9aCoeQed3btkDA= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:MWHPR10MB1389.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(346002)(136003)(376002)(366004)(396003)(39860400002)(2906002)(66556008)(478600001)(66476007)(16576012)(5660300002)(31696002)(6486002)(52116002)(2616005)(66946007)(44832011)(956004)(86362001)(316002)(8936002)(4326008)(36756003)(8676002)(83380400001)(16526019)(26005)(186003)(31686004)(53546011)(43740500002)(45980500001);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?a1BaQ0ZXdzF2SnRQdHIxNTQ2cTFSalZJU1lJeTBkNjY3cFVKWGd3a2lyditY?= =?utf-8?B?dkNybUR3NzBFczlNbkJRVEh6T1VjVXp1RlhMKzAvL0hoMW1Pakh2TFZJemFR?= =?utf-8?B?elJQaXhqWUYrb3RJM0FRM2V0VXBJQmdjdGtxd1h6VVhrTDdER3F2QjYxYWdw?= =?utf-8?B?WUhJVGFwKzlrVUtJMnoyQlF3cExCbldKK2t5U29qQkV0NHc1NHRZSkVzeThn?= =?utf-8?B?dW1JbnNaY0pzajFBYVYrN2JWanJ5eC9VUDduQWxrQmJRM085YWpPUVhnOW5N?= =?utf-8?B?b0g1dUhCYjVQOGVpaEFsdXF2M3FEN3BobHBoeWRGNm9UYkx4UThZbWE1eCto?= =?utf-8?B?TWExc1B1V1RyWENHTTVmMlBTdG1IK3B5MnRCangzR05lTXBJaFFkNDVHdms3?= =?utf-8?B?d2hEM1lua0tkVEp2dTUvcHU3SlJRdnlnV1FIOFhuQXJ3QkFlRWdjcHpVRGVv?= =?utf-8?B?S21OQU5EaUttMGxCYnQ1WUg1eHFYTGRWTXp1WlBicUpjTGVXOVcxT0dUQjJL?= =?utf-8?B?bkQ5NDFtK2Y1QjY5TURmNHgwME11bTVEdFFiNUhaWHQ0cnlJdk0wSGJPUjRm?= =?utf-8?B?RWp4RmpVM0toeHdCL2xzN0FjaHY0UUloRWpxVTFDNkd3YnJjN2UwTW5TRUQz?= =?utf-8?B?bzlkQWdmN0lLbHNPWmJDaVpqdEtGQ3JMSnYvUVJNTkxKc3FBZHhhdWhFbEdY?= =?utf-8?B?QWVhQ2Q5cDB2c084a3FxSytvVVB3dklkcFYyZU5UZ0FYUHVFZVJPQzZiTUZY?= =?utf-8?B?R2UrYWFZdGRHbGgxL083Z1p1S1l2MnZ2VGRBNFNGd3dvZThnaGoyMHRES3p1?= =?utf-8?B?OXNVYUgxVFlaSk5vZkIzeVhnVmV0YWhjS1dTV2FsVkRxNU1RVXBOZks5bE9I?= =?utf-8?B?TTlyREZ4aTIvTnZSZ2E0d1lzcU9peWJ3ZzJGUFdtQml1L1NUSVhOd2I3UFR5?= =?utf-8?B?RFAyZ1pIbzFLTGZEWmJzeW51TE92VXN5ZzM4L3FEbDkrSTVTaDlWaThFVTNE?= =?utf-8?B?c2JVTG9IditoOWViejVXNDRzKzA0c25nRENLOWV0V0U3WTIxYTJoTzhnTVFK?= =?utf-8?B?TWFCKzBOcUJLM2RMTzJWQmJsdXNWRUZITVZvekxyRVBTM1d4ajhkL2Q0Q040?= =?utf-8?B?NFFnU2hOL3dJemxaOGVnWkQ3OURkblBEVm5ocStNekdlUitMTVpjM1hFbUdu?= =?utf-8?B?WXpaN1VYeGl2UCtvTy9aSVoxZXRVeUx5aTR0Q1Q3dmhUVjlick1yakIvTG0r?= =?utf-8?B?WXQvRC8zTkFadDR1RUt4dUNTRHBjL0FRaG5LeU45QTlaNC9QOHEyMFVtbWlH?= =?utf-8?B?clNSakFDN3gwOWVGNjFibW1BNGpvOThpZmtDcUxWZmxESGU1eUNJaG55NUx2?= =?utf-8?B?V1hlQnBsb1BTVWQ5N0hLVFU2d0kwODF3c0hGN2lBSUoxemwvOXVTcnJoRmpK?= =?utf-8?Q?f2x5uL5W?= X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: 2c619f4e-d200-4dda-ba4f-08d8be3ecbd7 X-MS-Exchange-CrossTenant-AuthSource: MWHPR10MB1389.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Jan 2021 19:00:19.1797 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: Z0C/JkFAnu5ESlJtnccgtbCHjaCUjqdLXeM89ZzZ3N7E9YW6j8OjSAiWVp9L3IXdKa+INlvoVLBcjfp7tT7RPg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR1001MB2112 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9871 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 mlxscore=0 spamscore=0 suspectscore=0 phishscore=0 adultscore=0 mlxlogscore=999 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101210096 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9871 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 mlxscore=0 suspectscore=0 lowpriorityscore=0 bulkscore=0 adultscore=0 spamscore=0 phishscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101210096 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 1/20/21 1:23 AM, Miaohe Lin wrote: > The calculation 1U << (h->order + PAGE_SHIFT - 10) is actually equal to > (PAGE_SHIFT << (h->order)) >> 10. So we can make it more readable by > replace it with huge_page_size(h) / SZ_1K. > > Signed-off-by: Miaohe Lin > --- > fs/hugetlbfs/inode.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index 25c1857ff45d..f94b8f6553fa 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -1519,8 +1519,8 @@ static struct vfsmount *__init mount_one_hugetlbfs(struct hstate *h) > put_fs_context(fc); > } > if (IS_ERR(mnt)) > - pr_err("Cannot mount internal hugetlbfs for page size %uK", > - 1U << (h->order + PAGE_SHIFT - 10)); > + pr_err("Cannot mount internal hugetlbfs for page size %luK", > + huge_page_size(h) / SZ_1K); I appreciate the effort to make the code more readable. The existing calculation does take a minute to understand. However, it is correct and anyone modifying the code should be able to understand. With my compiler, your proposed change adds an additional instruction to the routine mount_one_hugetlbfs. I know this is not significant, but still it does increase the kernel size for a change that is of questionable value. In the kernel, size in KB is often calculated as (size << (PAGE_SHIFT - 10)). If you change the calculation in the hugetlb code to be: huge_page_size(h) << (PAGE_SHIFT - 10) my compiler will actually reduce the size of the routine by one instruction. -- Mike Kravetz > return mnt; > } > >