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=-6.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 D4C41C432BE for ; Fri, 6 Aug 2021 21:26:21 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1644C60EE4 for ; Fri, 6 Aug 2021 21:26:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 1644C60EE4 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 38D266B006C; Fri, 6 Aug 2021 17:26:20 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 33DDC8D0001; Fri, 6 Aug 2021 17:26:20 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1DD516B0072; Fri, 6 Aug 2021 17:26:20 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0239.hostedemail.com [216.40.44.239]) by kanga.kvack.org (Postfix) with ESMTP id F30A36B006C for ; Fri, 6 Aug 2021 17:26:19 -0400 (EDT) Received: from smtpin37.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 9466C18043080 for ; Fri, 6 Aug 2021 21:26:19 +0000 (UTC) X-FDA: 78445939278.37.64565B8 Received: from NAM10-DM6-obe.outbound.protection.outlook.com (mail-dm6nam10on2072.outbound.protection.outlook.com [40.107.93.72]) by imf03.hostedemail.com (Postfix) with ESMTP id 0A468300E039 for ; Fri, 6 Aug 2021 21:26:18 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Da87/1RqdvYH8vq3OSVP3yXypF+LrUSpUNBnOhi9oemrYUXUWNdW/5HvRQWNkyBQJIOm+zQOjdaey+4CojnBW1rSpB8uyocKnt7qeW6njiC8SKT+NWo1disRT3P642StmycWhbY3VkbqoeVifFSgBez9PqI9QtlwpnLvfIzHml7Su4i3A57YbzD6QB+N+5VLbOvuJ744jJ5uGk8I4DSO0lE2Cx6Moa0ZCuTTRDo2dVcvsaAZhPWFDavZ1vntJZoi6R6V6Kjp9/6ssS3TTzQA/YR6lk+7pdnmSYg4Sfw2G+glLiC+47y4HO6JmYw8++A+dOrJm9FLoQ52s90ogPax6w== 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=1bPPQGcp9xZfPIknp25xkrSOSMz0hiYT7Jk0PESQgNM=; b=e+fp3DwFGp3+wQl353h6Q7XOqKmMsHnSOse6Lc/PMaA8lUQ75qTR8qRFOMREgs+imXJ+dfF4pS5BBBCb/XMPO1rZu9kGFLGJDUqkNPbEEcGFdplg5Kb/bZDN3ODZJAZefqNt/eqISAPpLQm1V63YLHqEKsQKY3Zr2AOpTqqbZ1fGDNsU1TvwsXd505j8c+9y8MFW3IXf1p96rMI2YYHpEs5lpME/x7tzkN0+AWHZMK37E5ej11fxV+5XM/JMp7u4h79LmxA0ba0LJH5a/Nh/Vv0LheoAa+0fWYT8nuRqON6qFq1PvnoRwbbprohtUfOokVdK9c6doWNQzhGyrqiXAQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=1bPPQGcp9xZfPIknp25xkrSOSMz0hiYT7Jk0PESQgNM=; b=ahZB4j5TDa6yEOHEWd1zrJ28IElt5AdjYPi1uwMvrMS9QL2ct6he2IFWS3UJG19PPtNPsVqLWcFNU3Y8/P6JMhGROiP3bLY0Xz+nEPosJTcLSJH6buwVqAF58nAgxAhsCAV8k7sxE5qhmSc6Rf/LpfIEp94L9tMZSjmgtgV36rZMJWjCU/vN6DlQTO6TEbWKGhvkpaC3b4EHOKtRPSOkbk3IPq65Ld32MiI/Jqb1dRBtCL19IwWYKObaaLGXLA9RlPMgjvPwN7uifEOBFX5FOldrrLi7ET2AHUp96Un3lTiyqlGRY6vDl2HrVcfXjNu8cVwoN2LQxxKXt45UKZKLRQ== Received: from MN2PR12MB3823.namprd12.prod.outlook.com (2603:10b6:208:168::26) by MN2PR12MB4063.namprd12.prod.outlook.com (2603:10b6:208:1dc::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4394.15; Fri, 6 Aug 2021 21:26:15 +0000 Received: from MN2PR12MB3823.namprd12.prod.outlook.com ([fe80::dcee:535c:30e:95f4]) by MN2PR12MB3823.namprd12.prod.outlook.com ([fe80::dcee:535c:30e:95f4%6]) with mapi id 15.20.4394.017; Fri, 6 Aug 2021 21:26:15 +0000 From: Zi Yan To: Hugh Dickins Cc: Vlastimil Babka , David Hildenbrand , linux-mm@kvack.org, Matthew Wilcox , "Kirill A . Shutemov" , Mike Kravetz , Michal Hocko , John Hubbard , linux-kernel@vger.kernel.org, Roman Gushchin Subject: Re: [RFC PATCH 00/15] Make MAX_ORDER adjustable as a kernel boot time parameter. 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dkim=pass header.d=Nvidia.com header.s=selector2 header.b=ahZB4j5T; dmarc=pass (policy=quarantine) header.from=nvidia.com; spf=none (imf03.hostedemail.com: domain of ziy@nvidia.com has no SPF policy when checking 40.107.93.72) smtp.mailfrom=ziy@nvidia.com X-Stat-Signature: spzhfw4wbdj1n87ak6knjfsdk9d478fn X-HE-Tag: 1628285178-861339 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: --=_MailMate_F343033B-6EF6-4D7A-B403-0EF88D8B0BEB_= Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 6 Aug 2021, at 16:27, Hugh Dickins wrote: > On Fri, 6 Aug 2021, Zi Yan wrote: >> >> In addition, I would like to share more detail on my plan on supportin= g 1GB PUD THP. >> This patchset is the first step, enabling kernel to allocate 1GB pages= , so that >> user can get 1GB THPs from ZONE_NORMAL and ZONE_MOVABLE without using >> alloc_contig_pages() or CMA allocator. The next step is to improve ker= nel memory >> fragmentation handling for pages up to MAX_ORDER, since currently page= block size >> is still limited by memory section size. As a result, I will explore s= olutions >> like having additional larger pageblocks (up to MAX_ORDER) to counter = memory >> fragmentation. I will discover what else needs to be solved as I gradu= ally improve >> 1GB PUD THP support. > > Sorry to be blunt, but let me state my opinion: 2MB THPs have given and= > continue to give us more than enough trouble. Complicating the kernel'= s > mm further, just to allow 1GB THPs, seems a very bad tradeoff to me. I= > understand that it's an appealing personal project; but for the sake of= > of all the rest of us, please leave 1GB huge pages to hugetlbfs (until > the day when we are all using 2MB base pages). I do not agree with you. 2MB THP provides good performance, while letting= us keep using 4KB base pages. The 2MB THP implementation is the price we pay= to get the performance. This patchset removes the tie between MAX_ORDER and section size to allow >2MB page allocation, which is useful in many places. 1GB THP is one of the users. Gigantic pages also improve device performance, like GPUs (e.g., AMD GPUs can use any power of two up= to 1GB pages[1], which I just learnt). Also could you point out which part of my patchset complicates kernel=E2=80=99s mm? I could try to simplify i= t if possible. In addition, I am not sure hugetlbfs is the way to go. THP is managed by core mm, whereas hugetlbfs has its own code for memory management. As hugetlbfs gets popular, more core mm functionalities have been replicated and added to hugetlbfs codebase. It is not a good tradeoff either. One of the reasons I work on 1GB THP is that Roman from Facebook explicitly mentioned they want to use THP in place of hugetlbfs[2]. I think it might be more constructive to point out the existing issues in THP so that we can improve the code together. BTW, I am also working on simplifying THP code like generalizing THP split[3] and planning to simplify page table manipulation code by reviving Kirill=E2=80=99s idea[4= ]. [1] https://lore.kernel.org/linux-mm/bdec12bd-9188-9f3e-c442-aa33e25303a6= @amd.com/ [2] https://lore.kernel.org/linux-mm/20200903162527.GF60440@carbon.dhcp.t= hefacebook.com/ [3] https://lwn.net/Articles/837928/ [4] https://lore.kernel.org/linux-mm/20180424154355.mfjgkf47kdp2by4e@blac= k.fi.intel.com/ =E2=80=94 Best Regards, Yan, Zi --=_MailMate_F343033B-6EF6-4D7A-B403-0EF88D8B0BEB_= Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQJDBAEBCgAtFiEEh7yFAW3gwjwQ4C9anbJR82th+ooFAmENqPEPHHppeUBudmlk aWEuY29tAAoJEJ2yUfNrYfqKCyEP/ix8J88iwOdiEDae3kAkk/1mr8r/W6LWMfe0 VLAaYj7VuBBKUnAj4H6Mm2eQewPeO1SF1gYfqLp7AtKIFJcCuo6hZbQAW2VZ8cTX SMk4wimtoHItOFJKU1vVLbJSHfL15CQZT1G67nRHkANBMSmPkvp0ie/KhBMF3rU2 t6BQ6Tzt+utzzKIF+G3hJGYy5GM/v032DUMKrKhmaaJcs5NAVlObf5qEfl879khU 5+o041SvDqi7IyIkDqZM6SBVfmrHP5oIdZ2qx3vQ36OeWCJ0MvV0KvTXVwfBi7Bv wMHt11QQvdNJBn2ziDeHjBSELSaOvFC3ggiRuNf7EcbWMs1wsi2uiyI21G9kK3R+ lJiB8aZLksnEL3BeTrFslgZ2hFU9IDiaI2lgxbRf7ZQ9GkntHUYtC7VnBMfpyGKz gdHswp1VHrXTRNjzJgJ2A54eOhwztvEemQcMgR8NvGaOcO5760MHm6lSXGP4BMet xkSBSnLk0pIWg20NdJt+62aKfaWDr3JVGPqJTliq6Fht60Jo94nB+QyaBVXVwmXN MOkLSM0qnhi4VQXBzop8nD+JbDAG71df/KMuiwPz0eVSumntJg3+a5WtkkoEmKf7 CkBDfwjUcR8AFcUJpBGAm5S/zMxtCaVm6XAXu/cmvJeUYB3qeXJTd02bnFF181cA Sy73gMjV =ECSy -----END PGP SIGNATURE----- --=_MailMate_F343033B-6EF6-4D7A-B403-0EF88D8B0BEB_=--