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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_PASS autolearn=unavailable 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 B0679C10F11 for ; Thu, 25 Apr 2019 03:07:01 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7CB3F217FA for ; Thu, 25 Apr 2019 03:07:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="A35x/0Wb" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7CB3F217FA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=xuJT35k/W01QjB1/Iej55aB51ysrLTuL/VPZDioXbDg=; b=A35x/0Wb1ekUV5 HhSSGw7TPzoIssJD0Nek1kSs3HNFx5SmvHuDMElH1Mje2Nyc9RIe1j6rsa03sW5Jy4jb+5tqpNbxj XoGAGS8YylDyzgobFsSDMH5iDsyl+Hh5lxsN1MSULpG4Hk+4lWOnmhyGb/5R2hCtNg0151osn5MnQ fg7q//FOJACW6cul6YGTiXDWFWZjxmchA30bDR7TZo3Niljc0gnmljKbfh80q+DXR0My0psyFz3Zi ovbgs2CDkymQ6xMkcnYNKaGecCFi4FA05cuUFoDfBRd7YsLLDhMPcxRQWVicFeTiQvoAjM00i+gKZ 2HC4QtiZNoPOnd1b8K4g==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hJUiq-0000Z6-Jf; Thu, 25 Apr 2019 03:06:52 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hJUim-0000YP-BP for linux-arm-kernel@lists.infradead.org; Thu, 25 Apr 2019 03:06:50 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9920E374; Wed, 24 Apr 2019 20:06:45 -0700 (PDT) Received: from [10.163.1.68] (unknown [10.163.1.68]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CC24F3F5AF; Wed, 24 Apr 2019 20:06:35 -0700 (PDT) Subject: Re: [PATCH] arm64: configurable sparsemem section size To: Pavel Tatashin References: <20190423203843.2898-1-pasha.tatashin@soleen.com> <7f7499bd-8d48-945b-6d69-60685a02c8da@arm.com> From: Anshuman Khandual Message-ID: Date: Thu, 25 Apr 2019 08:36:38 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190424_200648_406582_4C1C8C23 X-CRM114-Status: GOOD ( 25.12 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michal Hocko , Takashi Iwai , catalin.marinas@arm.com, Dave Hansen , Will Deacon , Keith Busch , linux-mm , Yaowei Bai , Ross Zwisler , Sasha Levin , Dave Jiang , linux-nvdimm , Vishal L Verma , James Morris , "Huang, Ying" , Borislav Petkov , Tom Lendacky , Marc Zyngier , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , rppt@linux.vnet.ibm.com, Bjorn Helgaas , Dan Williams , linux-arm-kernel@lists.infradead.org, Ard Biesheuvel , sboyd@kernel.org, LKML , james.morse@arm.com, andrew.murray@arm.com, Andrew Morton , Fengguang Wu Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 04/25/2019 01:18 AM, Pavel Tatashin wrote: > On Wed, Apr 24, 2019 at 5:07 AM Anshuman Khandual > wrote: >> >> On 04/24/2019 02:08 AM, Pavel Tatashin wrote: >>> sparsemem section size determines the maximum size and alignment that >>> is allowed to offline/online memory block. The bigger the size the less >>> the clutter in /sys/devices/system/memory/*. On the other hand, however, >>> there is less flexability in what granules of memory can be added and >>> removed. >> >> Is there any scenario where less than a 1GB needs to be added on arm64 ? > > Yes, DAX hotplug loses 1G of memory without allowing smaller sections. > Machines on which we are going to be using this functionality have 8G > of System RAM, therefore losing 1G is a big problem. > > For details about using scenario see this cover letter: > https://lore.kernel.org/lkml/20190421014429.31206-1-pasha.tatashin@soleen.com/ Its loosing 1GB because devdax has 2M alignment ? IIRC from Dan's subsection memory hot add series 2M comes from persistent memory HW controller's limitations. Does that limitation applicable across all platforms including arm64 for all possible persistent memory vendors. I mean is it universal ? IIUC subsection memory hot plug series is still getting reviewed. Hence should not we wait for it to get merged before enabling applicable platforms to accommodate these 2M limitations. > >> >>> >>> Recently, it was enabled in Linux to hotadd persistent memory that >>> can be either real NV device, or reserved from regular System RAM >>> and has identity of devdax. >> >> devdax (even ZONE_DEVICE) support has not been enabled on arm64 yet. > > Correct, I use your patches to enable ZONE_DEVICE, and thus devdax on ARM64: > https://lore.kernel.org/lkml/1554265806-11501-1-git-send-email-anshuman.khandual@arm.com/ > >> >>> >>> The problem is that because ARM64's section size is 1G, and devdax must >>> have 2M label section, the first 1G is always missed when device is >>> attached, because it is not 1G aligned. >> >> devdax has to be 2M aligned ? Does Linux enforce that right now ? > > Unfortunately, there is no way around this. Part of the memory can be > reserved as persistent memory via device tree. > memory@40000000 { > device_type = "memory"; > reg = < 0x00000000 0x40000000 > 0x00000002 0x00000000 >; > }; > > pmem@1c0000000 { > compatible = "pmem-region"; > reg = <0x00000001 0xc0000000 > 0x00000000 0x80000000>; > volatile; > numa-node-id = <0>; > }; > > So, while pmem is section aligned, as it should be, the dax device is > going to be pmem start address + label size, which is 2M. The actual Forgive my ignorance here but why dax device label size is 2M aligned. Again is that because of some persistent memory HW controller limitations ? > DAX device starts at: > 0x1c0000000 + 2M. > > Because section size is 1G, the hotplug will able to add only memory > starting from > 0x1c0000000 + 1G Got it but as mentioned before we will have to make sure that 2M alignment requirement is universal else we will be adjusting this multiple times. > >> 27 and 28 do not even compile for ARM64_64_PAGES because of MAX_ORDER and >> SECTION_SIZE mismatch. Even with 27 bits its 128 MB section size. How does it solve the problem with 2M ? The patch just wanted to reduce the memory wastage ? > > Can you please elaborate what configs are you using? I have no > problems compiling with 27 and 28 bit. After applying your patch [1] on current mainline kernel [2]. $make defconfig CONFIG_ARM64_64K_PAGES=y CONFIG_ARM64_VA_BITS_48=y CONFIG_ARM64_VA_BITS=48 CONFIG_ARM64_PA_BITS_48=y CONFIG_ARM64_PA_BITS=48 CONFIG_ARM64_SECTION_SIZE_BITS=27 [1] https://patchwork.kernel.org/patch/10913737/ [2] git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git It fails with CC arch/arm64/kernel/asm-offsets.s In file included from ./include/linux/gfp.h:6, from ./include/linux/slab.h:15, from ./include/linux/resource_ext.h:19, from ./include/linux/acpi.h:26, from ./include/acpi/apei.h:9, from ./include/acpi/ghes.h:5, from ./include/linux/arm_sdei.h:14, from arch/arm64/kernel/asm-offsets.c:21: ./include/linux/mmzone.h:1095:2: error: #error Allocator MAX_ORDER exceeds SECTION_SIZE #error Allocator MAX_ORDER exceeds SECTION_SIZE _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel