From patchwork Wed Jul 29 03:34:18 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Justin He X-Patchwork-Id: 11690271 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6AA55722 for ; Wed, 29 Jul 2020 03:35:16 +0000 (UTC) Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (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 3DE892074B for ; Wed, 29 Jul 2020 03:35:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3DE892074B 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-nvdimm-bounces@lists.01.org Received: from ml01.vlan13.01.org (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id D6CAE11460B21; Tue, 28 Jul 2020 20:35:15 -0700 (PDT) Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=justin.he@arm.com; receiver= Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by ml01.01.org (Postfix) with ESMTP id 75F6B12693EC9 for ; Tue, 28 Jul 2020 20:35:13 -0700 (PDT) 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 309D631B; Tue, 28 Jul 2020 20:35:12 -0700 (PDT) Received: from localhost.localdomain (entos-thunderx2-02.shanghai.arm.com [10.169.212.213]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id A94CC3F66E; Tue, 28 Jul 2020 20:35:04 -0700 (PDT) From: Jia He To: Dan Williams , Vishal Verma , Mike Rapoport , David Hildenbrand Subject: [RFC PATCH 0/6] decrease unnecessary gap due to pmem kmem alignment Date: Wed, 29 Jul 2020 11:34:18 +0800 Message-Id: <20200729033424.2629-1-justin.he@arm.com> X-Mailer: git-send-email 2.17.1 Message-ID-Hash: JFWKKAKU6KNYZS5EZ74NWGMHA3FVWNJ7 X-Message-ID-Hash: JFWKKAKU6KNYZS5EZ74NWGMHA3FVWNJ7 X-MailFrom: justin.he@arm.com X-Mailman-Rule-Hits: nonmember-moderation X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation CC: Catalin Marinas , Will Deacon , Greg Kroah-Hartman , "Rafael J. Wysocki" , Andrew Morton , Steve Capper , Mark Rutland , Anshuman Khandual , Hsin-Yi Wang , Jason Gunthorpe , Dave Hansen , Kees Cook , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-mm@kvack.org, Pankaj Gupta , Kaly Xin , Jia He X-Mailman-Version: 3.1.1 Precedence: list List-Id: "Linux-nvdimm developer list." Archived-At: List-Archive: List-Help: List-Post: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 When enabling dax pmem as RAM device on arm64, I noticed that kmem_start addr in dev_dax_kmem_probe() should be aligned w/ SECTION_SIZE_BITS(30),i.e. 1G memblock size. Even Dan Williams' sub-section patch series [1] had been upstream merged, it was not helpful due to hard limitation of kmem_start: $ndctl create-namespace -e namespace0.0 --mode=devdax --map=dev -s 2g -f -a 2M $echo dax0.0 > /sys/bus/dax/drivers/device_dax/unbind $echo dax0.0 > /sys/bus/dax/drivers/kmem/new_id $cat /proc/iomem ... 23c000000-23fffffff : System RAM 23dd40000-23fecffff : reserved 23fed0000-23fffffff : reserved 240000000-33fdfffff : Persistent Memory 240000000-2403fffff : namespace0.0 280000000-2bfffffff : dax0.0 <- aligned with 1G boundary 280000000-2bfffffff : System RAM Hence there is a big gap between 0x2403fffff and 0x280000000 due to the 1G alignment. Without this series, if qemu creates a 4G bytes nvdimm device, we can only use 2G bytes for dax pmem(kmem) in the worst case. e.g. 240000000-33fdfffff : Persistent Memory We can only use the memblock between [240000000, 2ffffffff] due to the hard limitation. It wastes too much memory space. Decreasing the SECTION_SIZE_BITS on arm64 might be an alternative, but there are too many concerns from other constraints, e.g. PAGE_SIZE, hugetlb, SPARSEMEM_VMEMMAP, page bits in struct page ... Beside decreasing the SECTION_SIZE_BITS, we can also relax the kmem alignment with memory_block_size_bytes(). Tested on arm64 guest and x86 guest, qemu creates a 4G pmem device. dax pmem can be used as ram with smaller gap. Also the kmem hotplug add/remove are both tested on arm64/x86 guest. This patch series (mainly patch6/6) is based on the fixing patch, ~v5.8-rc5 [2]. [1] https://lkml.org/lkml/2019/6/19/67 [2] https://lkml.org/lkml/2020/7/8/1546 Jia He (6): mm/memory_hotplug: remove redundant memory block size alignment check resource: export find_next_iomem_res() helper mm/memory_hotplug: allow pmem kmem not to align with memory_block_size mm/page_alloc: adjust the start,end in dax pmem kmem case device-dax: relax the memblock size alignment for kmem_start arm64: fall back to vmemmap_populate_basepages if not aligned with PMD_SIZE arch/arm64/mm/mmu.c | 4 ++++ drivers/base/memory.c | 24 ++++++++++++++++-------- drivers/dax/kmem.c | 22 +++++++++++++--------- include/linux/ioport.h | 3 +++ kernel/resource.c | 3 ++- mm/memory_hotplug.c | 39 ++++++++++++++++++++++++++++++++++++++- mm/page_alloc.c | 14 ++++++++++++++ 7 files changed, 90 insertions(+), 19 deletions(-)