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 BF168CD4857 for ; Wed, 4 Sep 2024 16:02:02 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 544176B019E; Wed, 4 Sep 2024 12:02:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4F3856B0207; Wed, 4 Sep 2024 12:02:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 394A26B025B; Wed, 4 Sep 2024 12:02:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 1A7726B019E for ; Wed, 4 Sep 2024 12:02:02 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id AFCE3121496 for ; Wed, 4 Sep 2024 16:02:01 +0000 (UTC) X-FDA: 82527522042.21.C9B629E Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf11.hostedemail.com (Postfix) with ESMTP id E808540027 for ; Wed, 4 Sep 2024 16:01:53 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=none; spf=pass (imf11.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1725465638; 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; bh=w8LOziv7MozAmla7EABe1m8PyWPkOk1FeWVw/WFAy0o=; b=dQX5K2vNaK2Wiubf5tFfEQpIri9KlcztZz63P3eAEhuLeYRHbjEWf1uOwNCQ9HZtQy3e5Q d8If2B4YOTmVxHMVlFq+yPQqmRBXya+arQ3Gp+ibFbQyEkA4iQrkLwOjsItX+6qz9xEa6G fPuYl942AdzqHvDt0fH1CDDLvHeiw3g= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=none; spf=pass (imf11.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1725465638; a=rsa-sha256; cv=none; b=Yse9M6opkPmqNFPsZzubMRXTIo+ZTuPsmeyVcOeaLk6vUDK3iqOSoWBV5s7Tu9+83V9hv3 2YxPDY0g3WtZbw4pPi4U9s5XIY3QYohDV6nay8R42ewHdrPpeqU/m6d6OUUXDurDt8H8OK iy3u4jX6NmgPFjeVoYUimldhZmu/640= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3250FFEC; Wed, 4 Sep 2024 09:02:19 -0700 (PDT) Received: from [10.57.87.65] (unknown [10.57.87.65]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 84B9D3F73B; Wed, 4 Sep 2024 09:01:49 -0700 (PDT) Message-ID: <91a2d578-3ff2-41e1-a980-0d78c0663959@arm.com> Date: Wed, 4 Sep 2024 17:01:48 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/2] Do not shatter hugezeropage on wp-fault Content-Language: en-GB To: Dev Jain , akpm@linux-foundation.org, david@redhat.com, willy@infradead.org, kirill.shutemov@linux.intel.com Cc: anshuman.khandual@arm.com, catalin.marinas@arm.com, cl@gentwo.org, vbabka@suse.cz, mhocko@suse.com, apopple@nvidia.com, dave.hansen@linux.intel.com, will@kernel.org, baohua@kernel.org, jack@suse.cz, mark.rutland@arm.com, hughd@google.com, aneesh.kumar@kernel.org, yang@os.amperecomputing.com, peterx@redhat.com, ioworker0@gmail.com, jglisse@google.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240904100923.290042-1-dev.jain@arm.com> <2427338d-7be5-4939-8d01-6d99b9167fea@arm.com> <98f73b2f-ec1c-4e81-bfb2-6e02ebc4cdae@arm.com> From: Ryan Roberts In-Reply-To: <98f73b2f-ec1c-4e81-bfb2-6e02ebc4cdae@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: pj6x9u38i4kz5zkqrb5tsmpzf98eh8oo X-Rspam-User: X-Rspamd-Queue-Id: E808540027 X-Rspamd-Server: rspam02 X-HE-Tag: 1725465713-305187 X-HE-Meta: U2FsdGVkX1/XS55Y/rChFJP1Ad4JyN8biLH54xwEujGIAIriYdBWzUxOAa3DKg+FgNNKqFkojrqIHLvd0E3IEo0R6GgRRPNQuJrawy9UcbjkMzY0wNjvbJ8IrtNISDns4zO0h4+TtBja9u4JWqjLyKtUD8r0VcsHTZakNBUrmVZ0ObI+VoxBLOFsfWY0uBdCxvCQH+gBuUSsTMRyjf76fzj9uUU0tHeFIXib36uoLyz4rssKvnSWrz02HKoYzmK4YbMLTkV2ENIzT4z28ONSKUcgDNlbjpkR1hTifN3UJlNxK3dP4rS+F3VL9dOfCjFUIa8BUuPUMhq9rHajUlZz7Pz9hKLUnmSJ2GYF7QDbZh87LB9GaQuAdCmBpbgQtOX3VSUaw8l2mOlqlFkfF86mUgwB07yTRtiOSnP5w9qi5F4C6uFBeEBujMCi0W/0fR10APz6x+47TbPY9UjB+KHFMBRQ+nYQ+ywkhiMxtCjpjAOy05SjhnRnEkeRFzW30R66Io/XtywmUCtno+nBxbyWhZWpW1yEAXa5isgR3AvWOwTUhKvcSxLcJYWd5t1gLRyi1m6PO0z1FBUf3DNSrZGzjr0Ggu9KpGjLSYadfeU0Nl0JOHKq+uifOl2FLTAglnxqLnhTJEnv9OEP0RZuVydJiP6yPMg0bDY0BGTeeHti0SM5IscBPT9PVrCp2ilZqITO8uA7mfTBIIjkfUVw7G34paXJ825dPK1ywkGWf2NSsSTYDWHAIkHQQkN2FK8o9q6Ikz/gR1ztCe7TmkKaPd1rwHX2Gs1Xn2SvI225GGYrn79Y2pndnWvNerJdHfFLWBlAB7xdtpwGGe7Hml6vo/gQTLKHSDK9Aqs3D7BxgzcHjUbIkoWbTd2xZKecxTdIrpiwg2S/Ib6KFqhXT/Vf/ruIp7+aVZbybdNoXfyvOK8/Mqo7kIGuNUCs5YHsbXsSMlFHAgwmpemuyHcQg8PNRP4 I+wMECwy /PrsUPuCtnib5+Bp2CWiORK9sUk8l58exc6xqhEXjbEtN/Z1u7Zts4vO9XbiyfJjMxbIE+vAxQVW6m/o0IvFN0EEdAqjGhI2HSv0CRYtJEAgtLKRjzgMJidDI3kbU6ija8LzjC+FhWUNb8bJhPjmONcbUoaP9nZ2in7OLY8udBKYNWv6jwrSvkFuIC+JFTWbCuicYnHSWJ138ZL3TFqaF/HZ7OWSyGchzKj1u7wgxS9v3kUAUM1vHECGUljNQZaflSOxn 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: List-Subscribe: List-Unsubscribe: On 04/09/2024 16:41, Dev Jain wrote: > > On 9/4/24 17:06, Ryan Roberts wrote: >> Hi Dev, >> >> On 04/09/2024 11:09, Dev Jain wrote: >>> It was observed at [1] and [2] that the current kernel behaviour of >>> shattering a hugezeropage is inconsistent and suboptimal. For a VMA with >>> a THP allowable order, when we write-fault on it, the kernel installs a >>> PMD-mapped THP. On the other hand, if we first get a read fault, we get >>> a PMD pointing to the hugezeropage; subsequent write will trigger a >>> write-protection fault, shattering the hugezeropage into one writable >>> page, and all the other PTEs write-protected. The conclusion being, as >>> compared to the case of a single write-fault, applications have to suffer >>> 512 extra page faults if they were to use the VMA as such, plus we get >>> the overhead of khugepaged trying to replace that area with a THP anyway. >>> >>> Instead, replace the hugezeropage with a THP on wp-fault. >>> >>> v1->v2: >>>   - Wrap do_huge_zero_wp_pmd_locked() around lock and unlock >>>   - Call thp_fault_alloc() before do_huge_zero_wp_pmd_locked() to avoid >>>   - calling sleeping function from spinlock context >>> >>> [1]: https://lore.kernel.org/all/3743d7e1-0b79-4eaf-82d5-d1ca29fe347d@arm.com/ >>> [2]: https://lore.kernel.org/all/1cfae0c0-96a2-4308-9c62-f7a640520242@arm.com/ >>> >>> Dev Jain (2): >>>    mm: Abstract THP allocation >>>    mm: Allocate THP on hugezeropage wp-fault >>> >>>   include/linux/huge_mm.h |   6 ++ >>>   mm/huge_memory.c        | 171 +++++++++++++++++++++++++++++----------- >>>   mm/memory.c             |   5 +- >>>   3 files changed, 136 insertions(+), 46 deletions(-) >>> >> What is the base for this? It doesn't apply on top of mm-unstable. > > Sorry, forgot to mention, it applies on v6.11-rc5. Thanks, I'll give it a review tomorrow. Although I suspect that Andrew will want it based against mm-unstable once it gets into shape for merging. > >> >> Thanks, >> Ryan >>