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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9462EC02198 for ; Sat, 8 Feb 2025 17:40:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CC49F6B0088; Sat, 8 Feb 2025 12:40:55 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C4DF36B0089; Sat, 8 Feb 2025 12:40:55 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A52146B008A; Sat, 8 Feb 2025 12:40:55 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 87EBC6B0088 for ; Sat, 8 Feb 2025 12:40:55 -0500 (EST) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 1285316287A for ; Sat, 8 Feb 2025 17:40:55 +0000 (UTC) X-FDA: 83097492870.30.86FAB03 Received: from mx0a-00069f02.pphosted.com (mx0a-00069f02.pphosted.com [205.220.165.32]) by imf17.hostedemail.com (Postfix) with ESMTP id 782AA40013 for ; Sat, 8 Feb 2025 17:40:51 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2023-11-20 header.b=gL8KforI; dkim=fail ("body hash did not verify") header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=Xh09gsc+; dmarc=pass (policy=reject) header.from=oracle.com; arc=reject ("signature check failed: fail, {[1] = sig:microsoft.com:reject}"); spf=pass (imf17.hostedemail.com: domain of lorenzo.stoakes@oracle.com designates 205.220.165.32 as permitted sender) smtp.mailfrom=lorenzo.stoakes@oracle.com ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1739036451; a=rsa-sha256; cv=fail; b=VRcHL7KzfvpXBzIKnEaYroGwb3Jpe/yucAtvKWCMyf801PwVoLrqBUJEOaZMuPliPYVGiV 4RE1ycVBtYLojZZBKPm8VjjsHLnwh38488469R7+NI8ZCK/kSGNPwYaiU0e9WIoA2E11DP HVP+woNaLjDfOEBUi+4T+6lH5qBb2Kk= ARC-Authentication-Results: i=2; imf17.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2023-11-20 header.b=gL8KforI; dkim=fail ("body hash did not verify") header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=Xh09gsc+; dmarc=pass (policy=reject) header.from=oracle.com; arc=reject ("signature check failed: fail, {[1] = sig:microsoft.com:reject}"); spf=pass (imf17.hostedemail.com: domain of lorenzo.stoakes@oracle.com designates 205.220.165.32 as permitted sender) smtp.mailfrom=lorenzo.stoakes@oracle.com ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1739036451; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=+zga0xwWklmkTFlPhDZ7+eBIRp7gLcUrL1sKrQem6Cg=; b=kj2DfxgukrvOmnEkbVhCcgAoYY9uXKQMYtjIvhGVNRyT05WTYJprduXJ1LTtLyEx8Dm+h9 EIC8h/hGsUAA7/W5tc0PFX0VzmyvlmTcib2Rg8b7nD/16Lc0JJQomsjvUQEemzFhV5X/yw v5tR5Q2mcAMk4P+BAc7hFVodehVujtI= Received: from pps.filterd (m0246617.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 518HbCDV005534; Sat, 8 Feb 2025 17:40:49 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s= corp-2023-11-20; bh=+zga0xwWklmkTFlPhDZ7+eBIRp7gLcUrL1sKrQem6Cg=; b= gL8KforIdQTSwd+FabBuekjf2vKUfciw8GF6GW7dkYQSZ2SgqIbJ8uiEDihLB0Sx DfYPnmKHIY9kcX3VKsltk1WVO6MXA4fMopL3aOoI12uJToJFA4Uf5TIZGcuyKK8W yHAG70h/CBV8kp3DYwGjH6efQC3xoQ9F7OwYwDIZ8m3UCE2qU4SSGEYiK3PQzJTZ 83VSj+pi93PCtbxh4smLIWRw5WByzlitrAIUQDrXOV55CqCuu4aHX1dHtebhRKDo d7JYX8GhH8MpXfiAbXnNMoXY+b49QiLdAGig+GH8PomTLga/mI5cH7rS4LZWXBFN 07HlywfpxepM6ra0WCG88A== Received: from iadpaimrmta01.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta01.appoci.oracle.com [130.35.100.223]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 44p0tg0ddr-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sat, 08 Feb 2025 17:40:48 +0000 (GMT) Received: from pps.filterd (iadpaimrmta01.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by iadpaimrmta01.imrmtpd1.prodappiadaev1.oraclevcn.com (8.18.1.2/8.18.1.2) with ESMTP id 518EFF2U001994; Sat, 8 Feb 2025 17:40:47 GMT Received: from nam11-co1-obe.outbound.protection.outlook.com (mail-co1nam11lp2170.outbound.protection.outlook.com [104.47.56.170]) by iadpaimrmta01.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTPS id 44nwq5y1qm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sat, 08 Feb 2025 17:40:47 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=Ps+5WlNQpmI/XYtJIR5f4sGOknoILg97aK3Hbmn/14RvR8Q2fh55xrWQNVPx3ctDG+57XtDteQkUz1nYWPgwvKZJqX5jj2nMyCUenwv/lpRkiJ3pa9yzJlvnMiehbk4y76ntNSWHrdp7+iIei7ClrnT4+nlfGLmX1HAn2AkBuxGbs/Gp7sPd3Q6lCB7qevL50sogoNhQ33D/7okrNCtUy3Hbn2akdGs3K5cPW+cppVxPNwDtgjXx35pxa81HjfAjN7R06jfllSdWDjirWJryP4RP0D5QqHVN7Hx1ZXbWbRBYEkZWl5hrJGn+PuB6rB4M2No3wicNQ8WnSyAQhl+U8Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=SmQVWRkeoSecrLL+5msErTDsO1xXoMrDK4x/Iw/hq2Q=; b=VtiE9TEurq1wcT3BEgzGP8qFaKL6TfvLwWI2j7IRoR7cmf8ruwGPFgvVzzWSn5D6lfFTxvA0xn4YLeMp7b3+wvTihlPcwYf2OvQMxLQrt639ETXvJBS+1d7nnUxaAr1oz7Dd8SePxoCQM8ErZ8Ra8DXoR1CPq0FXicc9y3UYHd/2Bg8QOUBw47g5D4nLiCorPitVGh2cSMbmY6hWDORiZl6oljRniq91faV/EjhTJ1zATxB0Ect4bWge8uwRIBYCFK5n3Hf3eNfdZUbErQR1glxxD+OKKlS+llXtw+sHUPuO6JckZ0AdD109ZFCr0rMYkzrewL1QwZtqvOGd6Y7Ydg== 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=SmQVWRkeoSecrLL+5msErTDsO1xXoMrDK4x/Iw/hq2Q=; b=Xh09gsc+AT37ChiZFDUm3YkPXWa2l6xEK+fV7X9UFsiKVa67g0Tesa94sg7oHneMqdH++oGcOmAd53ScGKqk0wogZ/jAEHp65bm+peviNvDwnrCOYuxSSuisPzCPJQjoo1rbZLaQZ7iC3Nczeyl5ztVpJFS5nRjZiU54RdPg/6I= Received: from BYAPR10MB3366.namprd10.prod.outlook.com (2603:10b6:a03:14f::25) by LV3PR10MB8179.namprd10.prod.outlook.com (2603:10b6:408:28a::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8422.11; Sat, 8 Feb 2025 17:40:44 +0000 Received: from BYAPR10MB3366.namprd10.prod.outlook.com ([fe80::baf2:dff1:d471:1c9]) by BYAPR10MB3366.namprd10.prod.outlook.com ([fe80::baf2:dff1:d471:1c9%4]) with mapi id 15.20.8398.025; Sat, 8 Feb 2025 17:40:44 +0000 Date: Sat, 8 Feb 2025 17:40:41 +0000 From: Lorenzo Stoakes To: =?utf-8?B?SsO2cm4=?= Engel Cc: Uday Shankar , Muchun Song , Andrew Morton , linux-mm@kvack.org, "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Oscar Salvador Subject: Re: [bug report?] unintuitive behavior when mapping over hugepage-backed PROT_NONE regions Message-ID: <935c5dc8-03c6-4988-9bef-3c2de09e9efa@lucifer.local> References: <82afe852-4098-4eea-a646-37beab88604f@lucifer.local> Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: LO4P123CA0579.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:276::20) To BYAPR10MB3366.namprd10.prod.outlook.com (2603:10b6:a03:14f::25) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BYAPR10MB3366:EE_|LV3PR10MB8179:EE_ X-MS-Office365-Filtering-Correlation-Id: ddc78f3a-ad26-422d-15ff-08dd4867b6c1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|1800799024; X-Microsoft-Antispam-Message-Info: =?iso-8859-1?Q?Y0LLHFVEbCHBSPbApsSkpHvLl5Zwt/2jyRHrgInGx3zP0nJo5CfL0Y8K9t?= =?iso-8859-1?Q?E6zTxmc9PWqyPf9++VNOK9/8WyrK6W0Bxf+Ax4XhPHzxDC7n7P/CC+zrCm?= =?iso-8859-1?Q?3+doHvtydgOnBekzD/LP1wZ5kDAeJtUQ5pFlX66MvSh8WwOlSgxId/m0c3?= =?iso-8859-1?Q?bBzgksQD7UQjzci232Y/fCLPUEZqAjIQWA2EW+imy2xMl6HSQqjGOtE1wx?= =?iso-8859-1?Q?4DgjqaxJ5FVkaECrDsSHIi4YsXkad1p1FmfpvAE9ttVRcoBrJhHYTRq6rU?= =?iso-8859-1?Q?7bqb/WR6ettCL0mqt0NDhLUcP1wNw0bb30WisLvTdpdjgijFKn9Y67se6i?= =?iso-8859-1?Q?FKm5AtXdqmor+j2GvwHjIn5P13YZkfKdMHe6Pod13Uh49DmFz03s5G4v6d?= =?iso-8859-1?Q?ruXJb/Qi53CBoVSRW0lK0r+4vAFqgsGx6NGTBfRCcSKhO0NWGeadevFG2W?= =?iso-8859-1?Q?OyBxDogwhgVZYcHuwg0rLMNJC8m9WG5ZbA8hKcp7xR8cCV+yUE1vJLk+Q3?= =?iso-8859-1?Q?Hpp0+aIFxadix94zQaM+m0yWuYX2UfrQtZ/vjGtrD+YqA8OLrVpFhGt2ON?= =?iso-8859-1?Q?hShN/kIjf+kfFfNeO84MtcIka7blDgdzAYE8PmbAC/Du82jeGvCGNMtZko?= =?iso-8859-1?Q?RuJ31Ujy6yjajLt6n+vCmoATo0ughqk5ut5iZ9MnOyu58XTpbCfM9TKvj9?= =?iso-8859-1?Q?KIYPHc/Tiq6TgVxkbOUORAV/nWOlgblN22Owf+wAky1zebc8ueJbuFg8He?= =?iso-8859-1?Q?mUuSDRxkCsICOnP5uLHDzBfF4GzcR8zDskkYXnAr3WKlLSwgw1s1JwKxDO?= =?iso-8859-1?Q?G6etrx/SsvVeNWs8MfH5jMpQsdOfhSElfW4K6nOq955g3ykhOM++DK3lQQ?= =?iso-8859-1?Q?r+6NTmbdhyvLu2q+6nWP+GIrs+n8Lfy4qXEep478B3UkivdmJVSFf3axNY?= =?iso-8859-1?Q?mc6wHMEHKPSYULEBOkS9xCaGtUh+nweOUHRdu3RA5JnQuUXhWpHguXWDOX?= =?iso-8859-1?Q?mSRPQZtSUhKDcFuBoB7v0jVaM26c0uwgv38JkpnJa1HqnhXLSoR+W51Hqo?= =?iso-8859-1?Q?D5bWVV+M6uKsgNWk6SlRsVQ5do4JKjEcyKM9AvaipnHBKY076/dXhW2W+a?= =?iso-8859-1?Q?3M+8MKxEQpo/yAjyadaUX4EzG21UdWPK4keKLbAK5uWkDCXV/+3v20AAWI?= =?iso-8859-1?Q?PhZCvGRj1YUL7y5iUf3cOJICQbKoIlDcWugiA5mx6z2KaH5im85z4TMJq8?= =?iso-8859-1?Q?2I5sVZAnMfDgmkySpWYrW/EYvz7HZ10wlk21i4ZrayI74Hl3ZHHtMr2Gy8?= =?iso-8859-1?Q?q4TZ8WGUhjDUh/E8pzUjLmerIJFFvAZer/uGHVRGSovyg4B8aLADhSZ+h1?= =?iso-8859-1?Q?fv0FdGVadtM6OymUerE6fR956+tbjCMIn/9zbqJLtej5K0JEihD03a/d02?= =?iso-8859-1?Q?j7jfHK170LA5srJ7?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BYAPR10MB3366.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(376014)(1800799024);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?iso-8859-1?Q?eMLALrGioCJh53IRwLTXjRdik2Zi9weMJfZnA8t+B8Lx4EdhsZCbbuLjDJ?= =?iso-8859-1?Q?TwOrLavsTvtJlpyuN9WVVKVMzBJI4+nafGr/ps4zZZ294BgZ8lfDlXYTE2?= =?iso-8859-1?Q?3OVealqzW9nxaVsz1ZPP3GlrA/kB/FsZc/F9JwOzMqew/zs/J8T2+e8rYz?= =?iso-8859-1?Q?+LLJLaSmGdyUykm31bBp6m7tzbmGdg8h/DeYrW5TCsSSmipUcLdXPBKaMe?= =?iso-8859-1?Q?PwPGlqhh4mTZGYfoa+nfQjfC4XsmKhnKlnmTWZvvWjV2G10MZ53dMKpt4Y?= =?iso-8859-1?Q?Sue00GFW54OIARH+tTws2VCK9p60QwoiFdb+F6HA7/aRuugbfLW2Gcx4mK?= =?iso-8859-1?Q?EpgeU2/QyJvofNBgS+a5NsAO6ieJkiIStE9P5pDEpCiTWUxwbNdIFHZ8Ge?= =?iso-8859-1?Q?TJRuHrDqPnPgMVO/eKf0cQrme5Ahq7jIjgg/VvRmXUvB9G0LHPNRrNTJP4?= =?iso-8859-1?Q?QtXtrdbRzQbh9WifeIrUYP3X2W5BKzXzO7ilnwCLjaKb1V82LJnmsN6Zbc?= =?iso-8859-1?Q?5+xH9vooGHSNDib0YzFeBwo2XKhsseGU4Ez3K6ppJtgUwFslEqes7Bp/16?= =?iso-8859-1?Q?wbyD5t+H54geKAAYrFox2/uMsw4RJFgrjPO3SzMwm7YcmbAPhN1s6/Fth3?= =?iso-8859-1?Q?DiIhaoSQoSzDSqy/4gqtk8cWoWZi0p47rKrxWjCFBDfl27gwkGKONsDL72?= =?iso-8859-1?Q?CH4hgrz2DdVCqJrS4Fr6A2IEB1tr4Vz8pV+6W89joQ0uwHMaRxMc5PWkpg?= =?iso-8859-1?Q?JveyxElrJjy4gemK2ki5hO2w6UCB4TT5Dgf8lIP4UCdzSAUV5gCZetOjki?= =?iso-8859-1?Q?Qldu6RLRT72v57w71oIR28rHzdC5O0+XGqr2zWn921kUtRExnPds2DiprH?= =?iso-8859-1?Q?MZcza7biXyrCL7UBUsJBfhuPhDzPHY8cchFeJImV5ScBM7x8p7/i0R1IEY?= =?iso-8859-1?Q?sRN5DgaZBt61hrFOxQ4d5l3SuJa4fETUZZIHxvGNPxWqgz3WCBVTCvnQEz?= =?iso-8859-1?Q?GK9rCB9j1x4PKlehBoD5KMB4RNu06AKPDNBopG14fWBjgIcfdepsgssXB0?= =?iso-8859-1?Q?hbTdRXjoXGgR+fPMnGGPhI2SKUu5bi0l+7VeiE6SEzTYkQuVFakHpfYhff?= =?iso-8859-1?Q?E/OlZr95SIUqRw9T/QkEq+FA2il0eBrgtnbIYyRW0Ox6zQoKFykywwPWvH?= =?iso-8859-1?Q?KXegdv5wyrNmPIu/7nah7qj/uejJY6NH7WoTU9K/UR2D+FUilrZdOmpKgP?= =?iso-8859-1?Q?xeTCSwjNbMrTGGypLYESdAk+weMauNPbczIO4pVh8P5OYIR29gg5LTzr2F?= =?iso-8859-1?Q?l9Eu+XeIyJ5Q7hexKbsMAhxO5jXlXO0j+GgSDe2FyleV/CuE4hY0MjtDjA?= =?iso-8859-1?Q?suI0CgHnlLQu/5/Tlimv6J9aEAZ0kx9gkCxYv6ctTT+SnP6S/nxgpHKr/w?= =?iso-8859-1?Q?bxCSw4NbB7Zh9oGAES2WMPjtnrOi01zSOeiq3df3Z8MfZS0kyEcNoSFJ2e?= =?iso-8859-1?Q?SJwC8a7Mg+gdtUNdGaoCNsPksCl5Ktc8ZAg4M+0acQLflp3C66mQrBA8Wo?= =?iso-8859-1?Q?FpG1m0fyq1hTe0P4DqMQfUbMu6pjkV7trdgdhV+5x+9lfA5Phps31sjO2G?= =?iso-8859-1?Q?W7ZhThLqLKOUczv/WKtUzYnhPzW51OvuZVZB0icAjHd3ypEqlVW2mBCg?= =?iso-8859-1?Q?=3D=3D?= X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: /PAc0fyWmFEWyIqBDTjqRFU9T+rAXRTC4HonNE7W/yrQnLyvDfzH2FEwp7qGnDornp51HoQmHkjKQIMJguopNLim8dYNM5O22+VzGyIz5JaeZ0NyQic/Wxf1d7Bv/ElkxGTiK5xZnZl/CNOUmhpNgK1PhqukVZH0eqDpNru+se9r4at0ryjj8NuJBVgFkcojHvRBGqryRlROHxFOnVqlvp2yXqtrTLnaLF94yiLd3AnTfah0OmS2EQuDAECosfLwFLQUbz62z5YRp/uniy2h4crWrcbRO6pIuEBgAY//4opXx0/d+vfEZbogiZRkvGGHD1eaJm4ZAo+cK2lspjSCe0rz0QOMTUzA8itO1P6qewPsJXLl8NXJ4PNif/C7eQzMNtNbgsEt9VrgsVugirlQb3s76LjNkOVUZfEpBRVFejOwCp/qWOZnU9PnKjdUw8ZTYhxWYeThJnJBLR4R6nmjpf6rtEkbFdo9qqm4BDuVnP+lIQ/mOGmSi8YB1bdL2TFG5i+OKoM4AYZK29c3D6SPySnr6RajebX+p2aHSQ+UlWf9z8hLSYaPpLzsOxW0EaW+f9k+rss0b8r4NWhXmmkth0PNTWZzt+RtZ2sVxlpsGZY= X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: ddc78f3a-ad26-422d-15ff-08dd4867b6c1 X-MS-Exchange-CrossTenant-AuthSource: BYAPR10MB3366.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Feb 2025 17:40:44.3246 (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: Fq5seoKKPJBii1pGVEKa4oRpCJbOCPSjwwRJ9dCJtN3gV3VzNQmp4PXwSAzzxVVkjnseVO04q+gnREiSe8HD7/mSQM5b9fHu70aXJwBl1QY= X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV3PR10MB8179 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-08_08,2025-02-07_03,2024-11-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxscore=0 mlxlogscore=999 phishscore=0 bulkscore=0 malwarescore=0 adultscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2501170000 definitions=main-2502080149 X-Proofpoint-GUID: Khit3nVFDJyPCqZOhepQwbnER_v6wZ_N X-Proofpoint-ORIG-GUID: Khit3nVFDJyPCqZOhepQwbnER_v6wZ_N X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 782AA40013 X-Stat-Signature: ih56nxro91d57rghy4kruubd8g64e5we X-Rspam-User: X-HE-Tag: 1739036451-241434 X-HE-Meta: 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 XGZkxrBq 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.042774, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, Feb 08, 2025 at 09:37:34AM -0800, Jörn Engel wrote: > On Sat, Feb 08, 2025 at 04:02:47PM +0000, Lorenzo Stoakes wrote: > > > > To be clear, you won't get any kind of undefined behaviour (what that means > > wrt the kernel is not entirely clear - but if it were to mean as equivalent > > to the compiler sort 'anything might happen' - then no) or incomplete state. > > Going off on that tangent, I think compiler folks completely abuse > undefined behavior. Historically it simply meant that you might get two > or more different (and well-defined) results, depending on which > specific hardware you ran on. Somehow that was reinterpreted as "I have > license to do whatever I want". > > > > I guess you mean PROT_NONE? :) For the case in the thread you would have to > > have mapped a hugetlb area over the PROT_NONE one without MAP_NORESERVE and > > with insufficiently reserved hugetlb pages, a combination which should be > > expected to possibly fail. > > > > If you perform an mprotect() to R/W the range, you will end up with a 'one > > and done' operation. > > > > I'd also suggest that hugetlb doesn't seem to fit a malloc library like to > > me, as you rely on reserved pages, rather wouldn't it make more sense to > > try to allocate memory that gets THP pages? You could MADV_COLLAPSE to try > > to make sure... > > > > However, if aligned correctly, we should automagically give you those. > > We tried THP around 2012 and rejected it. The latency tail became a lot > longer and fatter. Various things have changed that might make THP less > bad today, but I am not aware of anyone reevaluating it. A _lot_ has changed. Try it again :) > > I think the problem with THP was the mmap_sem. Given a heavily threaded > process, the mmap_sem tends to be the one dominant lock in the kernel. A lot of work has been done on reducing mmap_sem contention. Again, worth another shot ;) > > A secondary problem might have been the background thread scanning for > pages that can be merged. Not sure about this part. We just disabled > THP and moved on to other problems. This sounds like really ancient problems that no longer exist (as well as a lot of FUD about THP at the time actually). We tend to proactively go THP if we can these days. > > > And yes, PROT_NONE/PROT_RW. Sorry! Haha no problem, just to clarify I understood you! > > Jörn > > -- > Every hour workers spend doing something else is an hour that they > aren't doing their jobs. > -- unknown >