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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 71E45C433E0 for ; Mon, 8 Feb 2021 04:40:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 02DAA64E6A for ; Mon, 8 Feb 2021 04:40:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 02DAA64E6A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6C6FC6B006C; 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Sun, 7 Feb 2021 20:40:11 -0800 (PST) Received: from [192.168.0.130] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 60FB63F719; Sun, 7 Feb 2021 20:40:05 -0800 (PST) Subject: Re: [RFC 0/3] mm/page_alloc: Fix pageblock_order with HUGETLB_PAGE_SIZE_VARIABLE To: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, akpm@linux-foundation.org Cc: Will Deacon , Robin Murphy , Marek Szyprowski , Christoph Hellwig , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Michal Hocko , Vlastimil Babka , Mike Kravetz , Matthew Wilcox References: <1612422084-30429-1-git-send-email-anshuman.khandual@arm.com> From: Anshuman Khandual Message-ID: <4e90b823-0f36-3dc6-fd00-e5ba27590550@arm.com> Date: Mon, 8 Feb 2021 10:10:34 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <1612422084-30429-1-git-send-email-anshuman.khandual@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 82DDDC0001DE X-Stat-Signature: 5y7jonyr5abs44dknfxdijgcfax578n1 Received-SPF: none (arm.com>: No applicable sender policy available) receiver=imf06; identity=mailfrom; envelope-from=""; helo=foss.arm.com; client-ip=217.140.110.172 X-HE-DKIM-Result: none/none X-HE-Tag: 1612759211-530608 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 2/4/21 12:31 PM, Anshuman Khandual wrote: > The following warning gets triggered while trying to boot a 64K page size > without THP config kernel on arm64 platform. > > WARNING: CPU: 5 PID: 124 at mm/vmstat.c:1080 __fragmentation_index+0xa4/0xc0 > Modules linked in: > CPU: 5 PID: 124 Comm: kswapd0 Not tainted 5.11.0-rc6-00004-ga0ea7d62002 #159 > Hardware name: linux,dummy-virt (DT) > [ 8.810673] pstate: 20400005 (nzCv daif +PAN -UAO -TCO BTYPE=--) > [ 8.811732] pc : __fragmentation_index+0xa4/0xc0 > [ 8.812555] lr : fragmentation_index+0xf8/0x138 > [ 8.813360] sp : ffff0000864079b0 > [ 8.813958] x29: ffff0000864079b0 x28: 0000000000000372 > [ 8.814901] x27: 0000000000007682 x26: ffff8000135b3948 > [ 8.815847] x25: 1fffe00010c80f48 x24: 0000000000000000 > [ 8.816805] x23: 0000000000000000 x22: 000000000000000d > [ 8.817764] x21: 0000000000000030 x20: ffff0005ffcb4d58 > [ 8.818712] x19: 000000000000000b x18: 0000000000000000 > [ 8.819656] x17: 0000000000000000 x16: 0000000000000000 > [ 8.820613] x15: 0000000000000000 x14: ffff8000114c6258 > [ 8.821560] x13: ffff6000bff969ba x12: 1fffe000bff969b9 > [ 8.822514] x11: 1fffe000bff969b9 x10: ffff6000bff969b9 > [ 8.823461] x9 : dfff800000000000 x8 : ffff0005ffcb4dcf > [ 8.824415] x7 : 0000000000000001 x6 : 0000000041b58ab3 > [ 8.825359] x5 : ffff600010c80f48 x4 : dfff800000000000 > [ 8.826313] x3 : ffff8000102be670 x2 : 0000000000000007 > [ 8.827259] x1 : ffff000086407a60 x0 : 000000000000000d > [ 8.828218] Call trace: > [ 8.828667] __fragmentation_index+0xa4/0xc0 > [ 8.829436] fragmentation_index+0xf8/0x138 > [ 8.830194] compaction_suitable+0x98/0xb8 > [ 8.830934] wakeup_kcompactd+0xdc/0x128 > [ 8.831640] balance_pgdat+0x71c/0x7a0 > [ 8.832327] kswapd+0x31c/0x520 > [ 8.832902] kthread+0x224/0x230 > [ 8.833491] ret_from_fork+0x10/0x30 > [ 8.834150] ---[ end trace 472836f79c15516b ]--- > > This warning comes from __fragmentation_index() when the requested order > is greater than MAX_ORDER. > > static int __fragmentation_index(unsigned int order, > struct contig_page_info *info) > { > unsigned long requested = 1UL << order; > > if (WARN_ON_ONCE(order >= MAX_ORDER)) <===== Triggered here > return 0; > > Digging it further reveals that pageblock_order has been assigned a value > which is greater than MAX_ORDER failing the above check. But why this > happened ? Because HUGETLB_PAGE_ORDER for the given config on arm64 is > greater than MAX_ORDER. > > The solution involves enabling HUGETLB_PAGE_SIZE_VARIABLE which would make > pageblock_order a variable instead of constant HUGETLB_PAGE_ORDER. But that > change alone also did not really work as pageblock_order still got assigned > as HUGETLB_PAGE_ORDER in set_pageblock_order(). HUGETLB_PAGE_ORDER needs to > be less than MAX_ORDER for its appropriateness as pageblock_order otherwise > just fallback to MAX_ORDER - 1 as before. While here it also fixes a build > problem via type casting MAX_ORDER in rmem_cma_setup(). > > This series applies in v5.11-rc6 and has been slightly tested on arm64. But > looking for some early feedbacks particularly with respect to concerns in > subscribing HUGETLB_PAGE_SIZE_VARIABLE on a platform where the hugetlb page > size is config dependent but not really a runtime variable. Even though it > appears that HUGETLB_PAGE_SIZE_VARIABLE is used only while computing the > pageblock_order, could there be other implications ? > > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Robin Murphy > Cc: Marek Szyprowski > Cc: Christoph Hellwig > Cc: Andrew Morton > Cc: linux-arm-kernel@lists.infradead.org > Cc: iommu@lists.linux-foundation.org > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org Probably missed some more folks, adding them here. + Michal Hocko + Vlastimil Babka + Mike Kravetz + Matthew Wilcox