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=-5.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,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 D776CC433DB for ; Fri, 12 Feb 2021 07:02:34 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7CEE564E56 for ; Fri, 12 Feb 2021 07:02:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7CEE564E56 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 1A6088D0025; 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Thu, 11 Feb 2021 23:02:32 -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 313123F73D; Thu, 11 Feb 2021 23:02:27 -0800 (PST) From: Anshuman Khandual Subject: Re: [PATCH 0/3] mm/page_alloc: Fix pageblock_order with HUGETLB_PAGE_SIZE_VARIABLE To: David Hildenbrand , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, akpm@linux-foundation.org, will@kernel.org Cc: Robin Murphy , Marek Szyprowski , Christoph Hellwig , Mark Rutland , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <1613024531-19040-1-git-send-email-anshuman.khandual@arm.com> <683c812a-ce3d-ef74-10d1-eaf8a3ae93d4@redhat.com> Message-ID: Date: Fri, 12 Feb 2021 12:32:56 +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: <683c812a-ce3d-ef74-10d1-eaf8a3ae93d4@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 3D5E8A0009D1 X-Stat-Signature: 3j9pg1qajyy9576w3d7p6ysfwipqwq13 Received-SPF: none (arm.com>: No applicable sender policy available) receiver=imf07; identity=mailfrom; envelope-from=""; helo=foss.arm.com; client-ip=217.140.110.172 X-HE-DKIM-Result: none/none X-HE-Tag: 1613113352-63014 Content-Transfer-Encoding: quoted-printable 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 2/11/21 2:07 PM, David Hildenbrand wrote: > On 11.02.21 07:22, Anshuman Khandual wrote: >> The following warning gets triggered while trying to boot a 64K page s= ize >> without THP config kernel on arm64 platform. >> >> WARNING: CPU: 5 PID: 124 at mm/vmstat.c:1080 __fragmentation_index+0xa= 4/0xc0 >> Modules linked in: >> CPU: 5 PID: 124 Comm: kswapd0 Not tainted 5.11.0-rc6-00004-ga0ea7d6200= 2 #159 >> Hardware name: linux,dummy-virt (DT) >> [=C2=A0=C2=A0=C2=A0 8.810673] pstate: 20400005 (nzCv daif +PAN -UAO -T= CO BTYPE=3D--) >> [=C2=A0=C2=A0=C2=A0 8.811732] pc : __fragmentation_index+0xa4/0xc0 >> [=C2=A0=C2=A0=C2=A0 8.812555] lr : fragmentation_index+0xf8/0x138 >> [=C2=A0=C2=A0=C2=A0 8.813360] sp : ffff0000864079b0 >> [=C2=A0=C2=A0=C2=A0 8.813958] x29: ffff0000864079b0 x28: 0000000000000= 372 >> [=C2=A0=C2=A0=C2=A0 8.814901] x27: 0000000000007682 x26: ffff8000135b3= 948 >> [=C2=A0=C2=A0=C2=A0 8.815847] x25: 1fffe00010c80f48 x24: 0000000000000= 000 >> [=C2=A0=C2=A0=C2=A0 8.816805] x23: 0000000000000000 x22: 0000000000000= 00d >> [=C2=A0=C2=A0=C2=A0 8.817764] x21: 0000000000000030 x20: ffff0005ffcb4= d58 >> [=C2=A0=C2=A0=C2=A0 8.818712] x19: 000000000000000b x18: 0000000000000= 000 >> [=C2=A0=C2=A0=C2=A0 8.819656] x17: 0000000000000000 x16: 0000000000000= 000 >> [=C2=A0=C2=A0=C2=A0 8.820613] x15: 0000000000000000 x14: ffff8000114c6= 258 >> [=C2=A0=C2=A0=C2=A0 8.821560] x13: ffff6000bff969ba x12: 1fffe000bff96= 9b9 >> [=C2=A0=C2=A0=C2=A0 8.822514] x11: 1fffe000bff969b9 x10: ffff6000bff96= 9b9 >> [=C2=A0=C2=A0=C2=A0 8.823461] x9 : dfff800000000000 x8 : ffff0005ffcb4= dcf >> [=C2=A0=C2=A0=C2=A0 8.824415] x7 : 0000000000000001 x6 : 0000000041b58= ab3 >> [=C2=A0=C2=A0=C2=A0 8.825359] x5 : ffff600010c80f48 x4 : dfff800000000= 000 >> [=C2=A0=C2=A0=C2=A0 8.826313] x3 : ffff8000102be670 x2 : 0000000000000= 007 >> [=C2=A0=C2=A0=C2=A0 8.827259] x1 : ffff000086407a60 x0 : 0000000000000= 00d >> [=C2=A0=C2=A0=C2=A0 8.828218] Call trace: >> [=C2=A0=C2=A0=C2=A0 8.828667]=C2=A0 __fragmentation_index+0xa4/0xc0 >> [=C2=A0=C2=A0=C2=A0 8.829436]=C2=A0 fragmentation_index+0xf8/0x138 >> [=C2=A0=C2=A0=C2=A0 8.830194]=C2=A0 compaction_suitable+0x98/0xb8 >> [=C2=A0=C2=A0=C2=A0 8.830934]=C2=A0 wakeup_kcompactd+0xdc/0x128 >> [=C2=A0=C2=A0=C2=A0 8.831640]=C2=A0 balance_pgdat+0x71c/0x7a0 >> [=C2=A0=C2=A0=C2=A0 8.832327]=C2=A0 kswapd+0x31c/0x520 >> [=C2=A0=C2=A0=C2=A0 8.832902]=C2=A0 kthread+0x224/0x230 >> [=C2=A0=C2=A0=C2=A0 8.833491]=C2=A0 ret_from_fork+0x10/0x30 >> [=C2=A0=C2=A0=C2=A0 8.834150] ---[ end trace 472836f79c15516b ]--- >> >> This warning comes from __fragmentation_index() when the requested ord= er >> is greater than MAX_ORDER. >> >> static int __fragmentation_index(unsigned int order, >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 struct contig_page_info *info) >> { >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 unsigned long request= ed =3D 1UL << order; >> >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (WARN_ON_ONCE(orde= r >=3D MAX_ORDER)) <=3D=3D=3D=3D=3D Triggered here >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 return 0; >> >> Digging it further reveals that pageblock_order has been assigned a va= lue >> 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 ass= igned >> as HUGETLB_PAGE_ORDER in set_pageblock_order(). HUGETLB_PAGE_ORDER nee= ds to >> be less than MAX_ORDER for its appropriateness as pageblock_order othe= rwise >> just fallback to MAX_ORDER - 1 as before. While here it also fixes a b= uild >> problem via type casting MAX_ORDER in rmem_cma_setup(). >=20 > I'm wondering, is there any real value in allowing FORCE_MAX_ZONEORDER = to be "11" with ARM64_64K_PAGES/ARM64_16K_PAGES? MAX_ORDER should be as high as would be required for the current config. Unless THP is enabled, there is no need for it to be any higher than 11. But I might be missing historical reasons around this as well. Probably others from arm64 could help here. >=20 > Meaning: are there any real use cases that actually build a kernel with= out TRANSPARENT_HUGEPAGE and with ARM64_64K_PAGES/ARM64_16K_PAGES? THP is always optional. Besides kernel builds without THP should always be supported. Assuming that all builds will have THP enabled, might not be accurate. >=20 > As builds are essentially broken, I assume this is not that relevant? O= r how long has it been broken? Git blame shows that it's been there for some time now. But how does that make this irrelevant ? A problem should be fixed nonetheless. >=20 > It might be easier to just drop the "TRANSPARENT_HUGEPAGE" part from th= e FORCE_MAX_ZONEORDER config. >=20 Not sure if it would be a good idea to unnecessarily have larger MAX_ORDE= R value for a given config. But I might be missing other contexts here.