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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 67F23C433DB for ; Fri, 29 Jan 2021 06:17:01 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BBEE664DFB for ; Fri, 29 Jan 2021 06:17:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BBEE664DFB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=bytedance.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CC27B6B0005; Fri, 29 Jan 2021 01:16:59 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C734A6B0006; Fri, 29 Jan 2021 01:16:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B61396B006C; Fri, 29 Jan 2021 01:16:59 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0100.hostedemail.com [216.40.44.100]) by kanga.kvack.org (Postfix) with ESMTP id 9F3F86B0005 for ; Fri, 29 Jan 2021 01:16:59 -0500 (EST) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 55F1A8249980 for ; Fri, 29 Jan 2021 06:16:59 +0000 (UTC) X-FDA: 77757804558.21.loaf80_57024a0275a6 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin21.hostedemail.com (Postfix) with ESMTP id 2DD85180442D3 for ; Fri, 29 Jan 2021 06:16:59 +0000 (UTC) X-HE-Tag: loaf80_57024a0275a6 X-Filterd-Recvd-Size: 6266 Received: from mail-pj1-f50.google.com (mail-pj1-f50.google.com [209.85.216.50]) by imf26.hostedemail.com (Postfix) with ESMTP for ; Fri, 29 Jan 2021 06:16:58 +0000 (UTC) Received: by mail-pj1-f50.google.com with SMTP id md11so5246493pjb.0 for ; Thu, 28 Jan 2021 22:16:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=IVLhRnuvVbWMIlCeZcR36K8LU3Zj15Td3oSsxTVm3dw=; b=Si4B7X6KLGW5Z89xZzVDHl7Skoe89UmiKGduLwtiFh0G2ErduZLcoyhzxfb8G5ThI4 syF50PNuDAMILs8Gbg3zVHAZgxzjYwu3Uw/rNASkDR2t4GqLp1BCz97iLqdk77dYA4c3 2CkKQdm+NEK6TlvP3w9vWyB3cGnovx1bDqRVEFI1RGuFthcCxJwnq2yoH7dGXiwhK+NG r0P2bc3WoSPjpzim4kOkGEgTHCPAxXV8ZbURzJNwTJ2lhdkX9bfbopWe/xjDpIAL3prB c/pTLgzzEXjCsYV5TlheMKOfuCAisunpmi0HckFP+fJtJ5ubMdQc7AsA3gMnJSt8Jmkw oBPA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=IVLhRnuvVbWMIlCeZcR36K8LU3Zj15Td3oSsxTVm3dw=; b=VwBKGAWPnNzmA3u+bJWpxYLfK7XkH21DMW2MzplUk3bw5C/Sk+MvnkLMZUu2wzXqG0 hfuJyfo5zs5ssoI0v8sjaXx+VvFrwp+j7a14ji+eRVpettiqW9mrsxIaTkgfj/11dabg 2r2XNl71cTdTD1PadkWc/Fi/T51mOOosSpXeOl9w2+h1SPgR/1ZOirnnJcF27eFhCzx5 9KTcLEnWyB1OlqjKQUhZxzGJby1moSF72mrXKdHpwdrMP3+DNuEsSzeYo8FMS89oVi0E AxcZHd+r7V2lLNrBkC9bYQinEkMVqZQZ5R6RMh13vABmdAcrpn3fEN6spsb/GDt3rPA+ V8fA== X-Gm-Message-State: AOAM532/1AQf9t/aM/KLn/Iv87Ft+JOnO4T6CCbh2FAzSa6XtZysyB8S itZncB8/AqTvjFyoAofEoRu/N7mxlbLEXoFc0kxGGA== X-Google-Smtp-Source: ABdhPJzlRocofXXUHhMpeg+wl6mPPzL5KoQPKYz1IbQOQ5+sTLmTyjhkh9y85ZPhI/SVxjYO862v/1WfnMigBDp1NyQ= X-Received: by 2002:a17:902:8503:b029:dc:44f:62d8 with SMTP id bj3-20020a1709028503b02900dc044f62d8mr2746955plb.34.1611901017151; Thu, 28 Jan 2021 22:16:57 -0800 (PST) MIME-Version: 1.0 References: <20210117151053.24600-1-songmuchun@bytedance.com> <20210117151053.24600-6-songmuchun@bytedance.com> <20210126092942.GA10602@linux> <6fe52a7e-ebd8-f5ce-1fcd-5ed6896d3797@redhat.com> <20210126145819.GB16870@linux> <259b9669-0515-01a2-d714-617011f87194@redhat.com> <20210126153448.GA17455@linux> <9475b139-1b33-76c7-ef5c-d43d2ea1dba5@redhat.com> <20210128222906.GA3826@localhost.localdomain> In-Reply-To: <20210128222906.GA3826@localhost.localdomain> From: Muchun Song Date: Fri, 29 Jan 2021 14:16:19 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v13 05/12] mm: hugetlb: allocate the vmemmap pages associated with each HugeTLB page To: Oscar Salvador Cc: David Hildenbrand , Jonathan Corbet , Mike Kravetz , Thomas Gleixner , mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, Peter Zijlstra , viro@zeniv.linux.org.uk, Andrew Morton , paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, Randy Dunlap , oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, Mina Almasry , David Rientjes , Matthew Wilcox , Michal Hocko , "Song Bao Hua (Barry Song)" , =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= , Xiongchun duan , linux-doc@vger.kernel.org, LKML , Linux Memory Management List , linux-fsdevel Content-Type: text/plain; charset="UTF-8" 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 Fri, Jan 29, 2021 at 6:29 AM Oscar Salvador wrote: > > On Wed, Jan 27, 2021 at 11:36:15AM +0100, David Hildenbrand wrote: > > Extending on that, I just discovered that only x86-64, ppc64, and arm64 > > really support hugepage migration. > > > > Maybe one approach with the "magic switch" really would be to disable > > hugepage migration completely in hugepage_migration_supported(), and > > consequently making hugepage_movable_supported() always return false. > > Ok, so migration would not fork for these pages, and since them would > lay in !ZONE_MOVABLE there is no guarantee we can unplug the memory. > Well, we really cannot unplug it unless the hugepage is not used > (it can be dissolved at least). > > Now to the allocation-when-freeing. > Current implementation uses GFP_ATOMIC(or wants to use) + forever loop. > One of the problems I see with GFP_ATOMIC is that gives you access > to memory reserves, but there are more users using those reserves. > Then, worst-scenario case we need to allocate 16MB order-0 pages > to free up 1GB hugepage, so the question would be whether reserves > really scale to 16MB + more users accessing reserves. > > As I said, if anything I would go for an optimistic allocation-try > , if we fail just refuse to shrink the pool. > User can always try to shrink it later again via /sys interface. Yeah. It seems that this is the easy way to move on. Thanks. > > Since hugepages would not be longer in ZONE_MOVABLE/CMA and are not > expected to be migratable, is that ok? > > Using the hugepage for the vmemmap array was brought up several times, > but that would imply fragmenting memory over time. > > All in all seems to be overly complicated (I might be wrong). > > > > Huge pages would never get placed onto ZONE_MOVABLE/CMA and cannot be > > migrated. The problem I describe would apply (careful with using > > ZONE_MOVABLE), but well, it can at least be documented. > > I am not a page allocator expert but cannot the allocation fallback > to ZONE_MOVABLE under memory shortage on other zones? > > > -- > Oscar Salvador > SUSE L3