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 8C78EC7619A for ; Wed, 5 Apr 2023 19:43:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AC3D86B0071; Wed, 5 Apr 2023 15:43:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A4D466B0074; Wed, 5 Apr 2023 15:43:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 879D86B0075; Wed, 5 Apr 2023 15:43:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 70E396B0071 for ; Wed, 5 Apr 2023 15:43:13 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 99FC6C10A7 for ; Wed, 5 Apr 2023 19:43:12 +0000 (UTC) X-FDA: 80648361024.05.F33A391 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by imf17.hostedemail.com (Postfix) with ESMTP id 85A334000B for ; Wed, 5 Apr 2023 19:43:08 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=IsY+qb58; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf17.hostedemail.com: domain of dan.j.williams@intel.com designates 134.134.136.24 as permitted sender) smtp.mailfrom=dan.j.williams@intel.com; arc=reject ("signature check failed: fail, {[1] = sig:microsoft.com:reject}") ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1680723789; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=m+M/EF5941BzIgLFdlij4tTUJKqlE4u5phY37m2giu0=; b=xg8+FgXOmeqWmyxRXkzrwujAQmRTyI/kqWeYuAvI1redDyhU2ho77ukZ12CBoF5h9vXX4s xUYN2To4smxWhgVpFLjSXE8cs/juAjwFPIEnRSTXMyD/BSwKBF9N++BuYm1JJzl+6Q/QNh PSXO3lllhulda4IiZv+W1KTeB41d0xQ= ARC-Authentication-Results: i=2; imf17.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=IsY+qb58; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf17.hostedemail.com: domain of dan.j.williams@intel.com designates 134.134.136.24 as permitted sender) smtp.mailfrom=dan.j.williams@intel.com; arc=reject ("signature check failed: fail, {[1] = sig:microsoft.com:reject}") ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1680723789; a=rsa-sha256; cv=fail; b=y5Ub4zvQfzc6gEbu5JgaiXmEUd6JHUnbTRAv1bhGTZL2PJ7jRoWu9FprvXPXBNPETQSMMS JMMKmaaq9R2694tIlu+32tgrv5FJKJslOPo/uz3kx8b63w2og2xpsLhAVApsGZNyw0oLwN wuq/fua1018vaw9yCTftnN8g3n0oB4E= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1680723788; x=1712259788; h=date:from:to:cc:subject:message-id:references: in-reply-to:mime-version; bh=JQDK/FAkxtiqZ/hepNLVP9tvi8je9quDwcL17OCVs9s=; b=IsY+qb58cXhoslH6JEvqkIf4PCn7cHA6FsHX1LcH88Fv+MMfilLLCR8c a+oA+17xcsc1XbDvh4AyuYtejHzxL3as0VahEj1sq0ZbKEIfJ1ei7aNtf klEgHXo1oGaxBBdvMu9RNIB96/jZQkRdEWq4Maz58w/VdRhHaumL0T7HV sZrRbY6hA4Uq5Y7uhjVxS8AHxL4NV9Zzoi2MNhcgyzIbE1Js8go0wuddo cGuPk6yRj8ue25vN5hLxO7PWO40CdDD7tjB1I8OssEU2OmM4JiD9H3KEQ z8c7TmvUh03OhET5camqBCvLhxTzgwxNTszMWor3gnHyLIG6M35j5DPmc A==; X-IronPort-AV: E=McAfee;i="6600,9927,10671"; a="344281772" X-IronPort-AV: E=Sophos;i="5.98,321,1673942400"; d="scan'208";a="344281772" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Apr 2023 12:43:06 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10671"; a="751381831" X-IronPort-AV: E=Sophos;i="5.98,321,1673942400"; d="scan'208";a="751381831" Received: from orsmsx603.amr.corp.intel.com ([10.22.229.16]) by fmsmga008.fm.intel.com with ESMTP; 05 Apr 2023 12:43:06 -0700 Received: from orsmsx612.amr.corp.intel.com (10.22.229.25) by ORSMSX603.amr.corp.intel.com (10.22.229.16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.21; Wed, 5 Apr 2023 12:43:05 -0700 Received: from orsmsx603.amr.corp.intel.com (10.22.229.16) by ORSMSX612.amr.corp.intel.com (10.22.229.25) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.21; Wed, 5 Apr 2023 12:43:05 -0700 Received: from ORSEDG602.ED.cps.intel.com (10.7.248.7) by orsmsx603.amr.corp.intel.com (10.22.229.16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.21 via Frontend Transport; Wed, 5 Apr 2023 12:43:05 -0700 Received: from NAM12-BN8-obe.outbound.protection.outlook.com (104.47.55.168) by edgegateway.intel.com (134.134.137.103) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.21; Wed, 5 Apr 2023 12:43:05 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=HBWvi2kDpw8dZLwVBAWXimmt05WADGJKMnK9zGnbgakYVjki+5xlgofZN5zf0d7+1XpZJBzykmrm/JMW+vZW0CXW9TKEWXvgS29T6AD55AlGPKzjuLxcm+UlKZhsSj/mHu80ABr9eonaLk3gCMMk/csJMd5FGbiLg8LgWeh/eKyHmEsKY9+6LvQgYyTnvxLyh2c7n2yy5LFrRugVlSPxvLZjZbndlLBEzBZyphiZFn5nhIy/OjBZcOVl7ScJZqpvOs+97P4V/lIK4f743DQCJlwOyf2MkNyVY9G0T9dM/1ggYnFiL94NAGFlwcEUbQg1mzVrLDl4ECIbLLFWV7XmPA== 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-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=m+M/EF5941BzIgLFdlij4tTUJKqlE4u5phY37m2giu0=; b=lmbWIf/00whNlbmrhPOe4BWs3gK80+ItZfJHLAFmkDI1OYkzNPuUNvyt8EattwArJ1AxAhTjZuXkDMjdrwsrAGsrzJ6c75MdeXvW5mXoOU+qJCzBT5GbZ8R1fch/AFk1tGmtGkjJtoRxLj0e1rVG8oQDyT9QkUjYMfZ/5S1RjppOm79ynzoTM6Xk9qVoYZz7MlBvYktkWjbsklBZf9m9qBLn0fL8PZHIrhHD9sUpfjsIsH9YWGIERoHoXe4/q0jOmRpt7abfbKbYtBLziESi9NaaUvq628OoWvay4HXLLUSvsA34t4xjtpw/ZPIN3Fd0jQPmCVgUB44QKlRC/RqbLg== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=intel.com; dmarc=pass action=none header.from=intel.com; dkim=pass header.d=intel.com; arc=none Received: from PH8PR11MB8107.namprd11.prod.outlook.com (2603:10b6:510:256::6) by IA1PR11MB6243.namprd11.prod.outlook.com (2603:10b6:208:3e7::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6254.35; Wed, 5 Apr 2023 19:43:01 +0000 Received: from PH8PR11MB8107.namprd11.prod.outlook.com ([fe80::ffa1:410b:20b3:6233]) by PH8PR11MB8107.namprd11.prod.outlook.com ([fe80::ffa1:410b:20b3:6233%5]) with mapi id 15.20.6254.033; Wed, 5 Apr 2023 19:43:00 +0000 Date: Wed, 5 Apr 2023 12:42:57 -0700 From: Dan Williams To: Matthew Wilcox , Dan Williams CC: Kyungsan Kim , , , , , , , , Subject: Re: Re: Re: RE(2): FW: [LSF/MM/BPF TOPIC] SMDK inspired MM changes for CXL Message-ID: <642dcf4169ae5_21a8294f@dwillia2-xfh.jf.intel.com.notmuch> References: <20230405020027.413578-1-ks0204.kim@samsung.com> <642cfda9ccd64_21a8294fd@dwillia2-xfh.jf.intel.com.notmuch> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: SJ0PR05CA0171.namprd05.prod.outlook.com (2603:10b6:a03:339::26) To PH8PR11MB8107.namprd11.prod.outlook.com (2603:10b6:510:256::6) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR11MB8107:EE_|IA1PR11MB6243:EE_ X-MS-Office365-Filtering-Correlation-Id: 23c8ecd1-ec7e-409f-376e-08db360df664 X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: VD9BNtx4kT7UrPLpf16l6gJaBJfZWyfpWBNudb6TR0cwV2Nlo/LQCr23IlaJC9zzImLM/7Q+DSWhaRnhuh+xbdkrqhSG1Vo+8GYGB0MNbsqB20hjIRoLybxqwkC1SJIBvP7RG12uclPiyHo23Fw5d1GyHqUaOTjc6SNsqXuZ3tqdn2QfDEO6cGjWGLmsJhGT1NznyFTQLNolYVh2l1/xmPRkAQClZIqS+9juSUH692QEo/EPmw/nK5P1PqDX+YyC5JtZ+uKNmEu6uWbMJoNFu3mshn9PS05g+Xp2aY8D7W5sr/Ti6MTEq4FwELKPBNeiYt7hHdtuElKonF9P6vy8h4HcirFyyOBrtjlHznxY+jb80NFpdhMdKp6rjMxfgWrUX/i05oPaYUJ6m57F/yeriffb0SzJg5rXQOyzHDIDsHYx2Mkz2fYZUMqv8aEH2fYiCMxVITekPl0uIhPaC9ILbjGtIXbGmukxCqL8s+EjCChwdjgTaBGbmCzX0+t5Ro8Fd04oohXGgf8sPjGrPt9k4ZnZfJdwaT7jQP6WNLr4ZywkPTrX6/nGeevAG/iWP15h X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:PH8PR11MB8107.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230028)(366004)(346002)(39860400002)(136003)(376002)(396003)(451199021)(478600001)(316002)(110136005)(66556008)(66476007)(66946007)(8676002)(9686003)(186003)(26005)(6506007)(6512007)(83380400001)(6486002)(4326008)(38100700002)(6666004)(86362001)(2906002)(8936002)(5660300002)(82960400001)(41300700001)(7416002);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?V9o52E1fanoaQRkHiRQH6WPRDG6drCtJIEWgEoaMxT2o5XN+HZSnkoPiRJFv?= =?us-ascii?Q?8c0TmNEdTqdJULbtHSchMW2rfoa60kwOzsMELfz1+tg5yeu6UQuR9vGHqwb7?= =?us-ascii?Q?EQ2zYGHk/x8WIm+SCqXmcHnm8Dmcsd8MvUP4+aDLtLt7aSephexuVo6wSF3K?= =?us-ascii?Q?6Fg8+aPxlx8GUv2OgvKJecfYzi9fIDbhLTskCN7/5f5nLWUzpDhrlWDl5egy?= =?us-ascii?Q?IPGTJ40mNZzWtxIPhg4amRq9cATHGWakD58E6Pwzn4Aq5w+e8HUdQYW4TTQm?= =?us-ascii?Q?hat8phHswi1E/Oincg8dMZhGA8nwEnHt43XgmXKaF18Ztg8vNj6ftr2yehFx?= =?us-ascii?Q?cdApMNY5bPulxB/dJ8M8Ny99PcLbxCFyZ69GpTuRRKec38zzgkdW+qLGF0eB?= =?us-ascii?Q?CPGNbAb0jDLQALxrh/5Bi5BBSryH5Au1JTdxlB9IW+dQ5vL9Izq7TDkANlnf?= =?us-ascii?Q?2hGN99224qZj9HYA1pfMK9PI1KrkCwuV4bxsWD0Lyl21/4rGgjuitV0u3M/q?= =?us-ascii?Q?cm3WinvpY66qpQzLKA3WjyBYe6WQy0+6ZpasbtChdSu2TG5GchteAEViUV5S?= =?us-ascii?Q?21gWsb5sxQOTmRlutKfUlYQKp4ksV78roT5FyxaXASrw6I9/cuys9DpP/taQ?= =?us-ascii?Q?XciHRsU7M0N+ZXMAPaiqCA8yE0HsGrUHX7Py/C2Fpsy1HvhgfUbTi494M1j1?= =?us-ascii?Q?lBGlHONWoB5Xdi++xEYcoUfOzfM5qydshdaX1ZPQLru3ciQoPBGOF6u+TSNj?= =?us-ascii?Q?fh5fef2VqV5lvQMNCYfrI+weLCpIcNYDTJesDAhkBVtmkl317jPBOqE4OCeG?= =?us-ascii?Q?yIgr8zU3wMvUYkr46oKwyai68FrNMc6NZFlmoliV0FpbH+R559Bttu6P7iPr?= =?us-ascii?Q?F1QUZgHlUCa7n2rPQm9ouZyOFOf6g/4v18YzQDu7o6xDou/K+WD6/bGNDZ0k?= =?us-ascii?Q?cN7Zw9D5eN+gZJwedyOzUnCmx6naKDDnZzzg6YaYrbkXY8rnR5+On78wQkgO?= =?us-ascii?Q?QaVl7hLhXM6Rmx9yRI8kw3fa+c+RDfJWSvgh7otcsKaj/k5BHOAwMJVZwAnl?= =?us-ascii?Q?Uflp1EfPY463DOu42pECzlY9gwKgnkJ1375iCkFymRSsS38e2a8nFsLr0tZ9?= =?us-ascii?Q?I6kZbesPS6PjVU+PiDgdG/Dxn8Isi5V9uMqcuvOL93CmuYpnN4+9jN0maj8O?= =?us-ascii?Q?aqQeXv9jU19T0VmtS8dvyMrLDV0ebfkp1ZQgownB0/CKtfxmxqisbPHI1Lv4?= =?us-ascii?Q?q4kwBCguIlwzqOqinqdxQ/ikZgZHtHyFdaia6C6uCUg9L1p6ptYm7mCCCb52?= =?us-ascii?Q?jVCLIZ4+H0/AkqOM0MODgOPy0S9y5NGfk9IaGpMi/J881xe9GbCb2bHOlrez?= =?us-ascii?Q?b4KLkyAnIgLYGiGl5x+qM7zBwTCEwkqVnBBkmoc9UoRgZYraDSfmQUD+9pky?= =?us-ascii?Q?nKc0Ha6rXiU5KqSqillrkfSue/m4kRF7F5Lq/3H8y0s3rAwGbBrOauTFFOnY?= =?us-ascii?Q?16fLyqpVAF9yy2BHKlj4d1neULAWC7sHo/D4dUHtE18egJDDVKWtLgp6CoO0?= =?us-ascii?Q?KVERe8VqDTMfOdlb73UuUgQKryB7TRWsv9N2hFgFcFZiN9qUDfSUGAWcMDBI?= =?us-ascii?Q?1g=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: 23c8ecd1-ec7e-409f-376e-08db360df664 X-MS-Exchange-CrossTenant-AuthSource: PH8PR11MB8107.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Apr 2023 19:43:00.1174 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: TO+xqSlch1nmI5j21JHBup/v3t6Bxu7zlxqL3tvJMmQdA/3o2Q54tjolSpOLglNbGB+VtyNBYiQbudS6uQxt4icjRb3ndHat+kOoat1riMU= X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR11MB6243 X-OriginatorOrg: intel.com X-Rspamd-Queue-Id: 85A334000B X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: gnfinto3w5ts8az3z7d5urduduhnrrtk X-HE-Tag: 1680723788-892895 X-HE-Meta: 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 e+JSDYJd NzEsb3TxrA11K1jLLAvsZuu53jsV8gXMTuIRDvNS34ewAjINOTYCTW3KcutbhN1mYewEeRB3LQqvB4AMILgzCCyzF+zVDS/zBAv5Q/aYGNK/+1dIvVd7jhdTKjzfY+eVbw8gGMfZkqlBJ5NfYXwZyrRypir74a2GpyQ3K1E/kdQQQTzR+y33JGQ/AF1wXp94gBeUjfxjIaRbN4a+RWEAlwDjeA/rbvT6j0zhwYHdld2H2vbKkWVz9gyS1VeOfgkrNracf/ppvnHKxu1r0eYGOuSUMt+XsR9nCaaaMRNff9O/B07Od+1A5UM1avDx1HSUGTVP9ejazrqPQJ6o= 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: Matthew Wilcox wrote: > On Tue, Apr 04, 2023 at 09:48:41PM -0700, Dan Williams wrote: > > Kyungsan Kim wrote: > > > We know the situation. When a CXL DRAM channel is located under ZONE_NORMAL, > > > a random allocation of a kernel object by calling kmalloc() siblings makes the entire CXL DRAM unremovable. > > > Also, not all kernel objects can be allocated from ZONE_MOVABLE. > > > > > > ZONE_EXMEM does not confine a movability attribute(movable or unmovable), rather it allows a calling context can decide it. > > > In that aspect, it is the same with ZONE_NORMAL but ZONE_EXMEM works for extended memory device. > > > It does not mean ZONE_EXMEM support both movability and kernel object allocation at the same time. > > > In case multiple CXL DRAM channels are connected, we think a memory consumer possibly dedicate a channel for movable or unmovable purpose. > > > > > > > I want to clarify that I expect the number of people doing physical CXL > > hotplug of whole devices to be small compared to dynamic capacity > > devices (DCD). DCD is a new feature of the CXL 3.0 specification where a > > device maps 1 or more thinly provisioned memory regions that have > > individual extents get populated and depopulated by a fabric manager. > > > > In that scenario there is a semantic where the fabric manager hands out > > 100G to a host and asks for it back, it is within the protocol that the > > host can say "I can give 97GB back now, come back and ask again if you > > need that last 3GB". > > Presumably it can't give back arbitrary chunks of that 100GB? There's > some granularity that's preferred; maybe on 1GB boundaries or something? The device picks a granularity that can be tiny per spec, but it makes the hardware more expensive to track in small extents, so I expect something reasonable like 1GB, but time will tell once actual devices start showing up. > > In other words even pinned pages in ZONE_MOVABLE are not fatal to the > > flow. Alternatively, if a deployment needs 100% guarantees that the host > > will return all the memory it was assigned when asked there is always > > the option to keep that memory out of the page allocator and just access > > it via a device. That's the role device-dax plays for "dedicated" memory > > that needs to be set aside from kernel allocations. > > > > This is to say something like ZONE_PREFER_MOVABLE semantics can be > > handled within the DCD protocol, where 100% unpluggability is not > > necessary and 97% is good enough. > > This certainly makes life better (and rather more like hypervisor > shrinking than like DIMM hotplug), but I think fragmentation may well > result in "only 3GB of 100GB allocated" will result in being able to > return less than 50% of the memory, depending on granule size and > exactly how the allocations got chunked. Agree.