From patchwork Fri Aug 6 12:47:06 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12423401 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=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 F3F0DC4338F for ; Fri, 6 Aug 2021 12:47:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 86046611B0 for ; Fri, 6 Aug 2021 12:47:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 86046611B0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id F23D18D0001; Fri, 6 Aug 2021 08:47:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id ED38D6B0071; Fri, 6 Aug 2021 08:47:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DC3AA8D0001; Fri, 6 Aug 2021 08:47:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0081.hostedemail.com [216.40.44.81]) by kanga.kvack.org (Postfix) with ESMTP id C3E446B006C for ; Fri, 6 Aug 2021 08:47:35 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 7CFB58249980 for ; Fri, 6 Aug 2021 12:47:35 +0000 (UTC) X-FDA: 78444632070.25.E0EE94E Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf13.hostedemail.com (Postfix) with ESMTP id 0B002100B6AF for ; Fri, 6 Aug 2021 12:47:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628254054; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=971GhShz25Kr5BT/yqIK2pAuLtt/U3ecg5I+mmxzob0=; b=C7lUokzjxdAMbLoqqe9EpvRvf655yQWkoH4igG/Ty5/2zCjfyNvJzXygMlLW0m9iJmUxy9 3mxp+gwuLhKb6s0TZNftkgEFZKZVNmaULgGQPsbgke2Dz+lH42//KiB/bDwwAN6N8ikTHi HKWCjwhf1Z/yAXK4pDYwQU2QLbD5BTo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-201-M9FlUlnAMRCzKX-mM45-aQ-1; Fri, 06 Aug 2021 08:47:33 -0400 X-MC-Unique: M9FlUlnAMRCzKX-mM45-aQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 06F2E1084F5F; Fri, 6 Aug 2021 12:47:30 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.192.224]) by smtp.corp.redhat.com (Postfix) with ESMTP id 16DFE5D6A1; Fri, 6 Aug 2021 12:47:16 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: David Hildenbrand , Andrew Morton , Vitaly Kuznetsov , "Michael S. Tsirkin" , Jason Wang , Marek Kedzierski , Hui Zhu , Pankaj Gupta , Wei Yang , Oscar Salvador , Michal Hocko , Dan Williams , Anshuman Khandual , Dave Hansen , Vlastimil Babka , Mike Rapoport , "Rafael J. Wysocki" , Len Brown , Pavel Tatashin , Greg Kroah-Hartman , virtualization@lists.linux-foundation.org, linux-mm@kvack.org, linux-acpi@vger.kernel.org Subject: [PATCH v3 0/9] mm/memory_hotplug: "auto-movable" online policy and memory groups Date: Fri, 6 Aug 2021 14:47:06 +0200 Message-Id: <20210806124715.17090-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 0B002100B6AF Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=C7lUokzj; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf13.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=david@redhat.com X-Stat-Signature: rba9q1hucy9oj5dg56hu37mejuz8h63h X-HE-Tag: 1628254054-759629 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: Hi, this series is based on v5.14-rc3, with [2] on top. I. Goal The goal of this series is improving in-kernel auto-online support. It tackles the fundamental problems that: 1) We can create zone imbalances when onlining all memory blindly to ZONE_MOVABLE, in the worst case crashing the system. We have to know upfront how much memory we are going to hotplug such that we can safely enable auto-onlining of all hotplugged memory to ZONE_MOVABLE via "online_movable". This is far from practical and only applicable in limited setups -- like inside VMs under the RHV/oVirt hypervisor which will never hotplug more than 3 times the boot memory (and the limitation is only in place due to the Linux limitation). 2) We see more setups that implement dynamic VM resizing, hot(un)plugging memory to resize VM memory. In these setups, we might hotplug a lot of memory, but it might happen in various small steps in both directions (e.g., 2 GiB -> 8 GiB -> 4 GiB -> 16 GiB ...). virtio-mem is the primary driver of this upstream right now, performing such dynamic resizing NUMA-aware via multiple virtio-mem devices. Onlining all hotplugged memory to ZONE_NORMAL means we basically have no hotunplug guarantees. Onlining all to ZONE_MOVABLE means we can easily run into zone imbalances when growing a VM. We want a mixture, and we want as much memory as reasonable/configured in ZONE_MOVABLE. Details regarding zone imbalances can be found at [1]. 3) Memory devices consist of 1..X memory block devices, however, the kernel doesn't really track the relationship. Consequently, also user space has no idea. We want to make per-device decisions. As one example, for memory hotunplug it doesn't make sense to use a mixture of zones within a single DIMM: we want all MOVABLE if possible, otherwise all !MOVABLE, because any !MOVABLE part will easily block the whole DIMM from getting hotunplugged. As another example, virtio-mem operates on individual units that span 1..X memory blocks. Similar to a DIMM, we want a unit to either be all MOVABLE or !MOVABLE. A "unit" can be thought of like a DIMM, however, all units of a virtio-mem device logically belong together and are managed (added/removed) by a single driver. We want as much memory of a virtio-mem device to be MOVABLE as possible. 4) We want memory onlining to be done right from the kernel while adding memory, not triggered by user space via udev rules; for example, this is reqired for fast memory hotplug for drivers that add individual memory blocks, like virito-mem. We want a way to configure a policy in the kernel and avoid implementing advanced policies in user space. The auto-onlining support we have in the kernel is not sufficient. All we have is a) online everything MOVABLE (online_movable) b) online everything !MOVABLE (online_kernel) c) keep zones contiguous (online). This series allows configuring c) to mean instead "online movable if possible according to the coniguration, driven by a maximum MOVABLE:KERNEL ratio" -- a new onlining policy. II. Approach This series does 3 things: 1) Introduces the "auto-movable" online policy that initially operates on individual memory blocks only. It uses a maximum MOVABLE:KERNEL ratio to make a decision whether a memory block will be onlined to ZONE_MOVABLE or not. However, in the basic form, hotplugged KERNEL memory does not allow for more MOVABLE memory (details in the patches). CMA memory is treated like MOVABLE memory. 2) Introduces static (e.g., DIMM) and dynamic (e.g., virtio-mem) memory groups and uses group information to make decisions in the "auto-movable" online policy across memory blocks of a single memory device (modeled as memory group). More details can be found in patch #3 or in the DIMM example below. 3) Maximizes ZONE_MOVABLE memory within dynamic memory groups, by allowing ZONE_NORMAL memory within a dynamic memory group to allow for more ZONE_MOVABLE memory within the same memory group. The target use case is dynamic VM resizing using virtio-mem. See the virtio-mem example below. I remember that the basic idea of using a ratio to implement a policy in the kernel was once mentioned by Vitaly Kuznetsov, but I might be wrong (I lost the pointer to that discussion). For me, the main use case is using it along with virtio-mem (and DIMMs / ppc64 dlpar where necessary) for dynamic resizing of VMs, increasing the amount of memory we can hotunplug reliably again if we might eventually hotplug a lot of memory to a VM. III. Target Usage The target usage will be: 1) Linux boots with "mhp_default_online_type=offline" 2) User space (e.g., systemd unit) configures memory onlining (according to a config file and system properties), for example: * Setting memory_hotplug.online_policy=auto-movable * Setting memory_hotplug.auto_movable_ratio=301 * Setting memory_hotplug.auto_movable_numa_aware=true 3) User space enabled auto onlining via "echo online > /sys/devices/system/memory/auto_online_blocks" 4) User space triggers manual onlining of all already-offline memory blocks (go over offline memory blocks and set them to "online") IV. Example For DIMMs, hotplugging 4 GiB DIMMs to a 4 GiB VM with a configured ratio of 301% results in the following layout: Memory block 0-15: DMA32 (early) Memory block 32-47: Normal (early) Memory block 48-79: Movable (DIMM 0) Memory block 80-111: Movable (DIMM 1) Memory block 112-143: Movable (DIMM 2) Memory block 144-275: Normal (DIMM 3) Memory block 176-207: Normal (DIMM 4) ... all Normal (-> hotplugged Normal memory does not allow for more Movable memory) For virtio-mem, using a simple, single virtio-mem device with a 4 GiB VM will result in the following layout: Memory block 0-15: DMA32 (early) Memory block 32-47: Normal (early) Memory block 48-143: Movable (virtio-mem, first 12 GiB) Memory block 144: Normal (virtio-mem, next 128 MiB) Memory block 145-147: Movable (virtio-mem, next 384 MiB) Memory block 148: Normal (virtio-mem, next 128 MiB) Memory block 149-151: Movable (virtio-mem, next 384 MiB) ... Normal/Movable mixture as above (-> hotplugged Normal memory allows for more Movable memory within the same device) Which gives us maximum flexibility when dynamically growing/shrinking a VM in smaller steps. V. Doc Update I'll update the memory-hotplug.rst documentation, once the overhaul [1] is usptream. Until then, details can be found in patch #2. VI. Future Work 1) Use memory groups for ppc64 dlpar 2) Being able to specify a portion of (early) kernel memory that will be excluded from the ratio. Like "128 MiB globally/per node" are excluded. This might be helpful when starting VMs with extremely small memory footprint (e.g., 128 MiB) and hotplugging memory later -- not wanting the first hotplugged units getting onlined to ZONE_MOVABLE. One alternative would be a trigger to not consider ZONE_DMA memory in the ratio. We'll have to see if this is really rrequired. 3) Indicate to user space that MOVABLE might be a bad idea -- especially relevant when memory ballooning without support for balloon compaction is active. v2 -> v3: - "mm/memory_hotplug: introduce "auto-movable" online policy" -- Fixup !CONFIG_CMA compilation issue - "drivers/base/memory: introduce "memory groups" to logically group memory blocks": Address Gregs feedback -- Rename and document group handling functions -- Store list of memory blocks instead of a reference count -- Return -EBUSY if memory_group_unregister() fails because there are still memory blocks added -- Document why memory_group_register() copies the given structure -- Simplify return handling in register memory_group_register() -- Document "struct memory_group" properly - Adjust other code to renamed group handling functions - Minor comment fixes and add some more comments v1 -> v2: - Split out all cleanup patches into [2] - Minor patch description updates - "dax/kmem: use a single static memory group for a single probed unit" -- Added Cc: Andrew Morton Cc: Vitaly Kuznetsov Cc: "Michael S. Tsirkin" Cc: Jason Wang Cc: Marek Kedzierski Cc: Hui Zhu Cc: Pankaj Gupta Cc: Wei Yang Cc: Oscar Salvador Cc: Michal Hocko Cc: Dan Williams Cc: Anshuman Khandual Cc: Dave Hansen Cc: Vlastimil Babka Cc: Mike Rapoport Cc: "Rafael J. Wysocki" Cc: Len Brown Cc: Pavel Tatashin Cc: Greg Kroah-Hartman Cc: virtualization@lists.linux-foundation.org Cc: linux-mm@kvack.org Cc: linux-acpi@vger.kernel.org [1] https://lkml.kernel.org/r/20210707073205.3835-1-david@redhat.com [2] https://lkml.kernel.org/r/20210712124052.26491-1-david@redhat.com David Hildenbrand (9): mm: track present early pages per zone mm/memory_hotplug: introduce "auto-movable" online policy drivers/base/memory: introduce "memory groups" to logically group memory blocks mm/memory_hotplug: track present pages in memory groups ACPI: memhotplug: use a single static memory group for a single memory device dax/kmem: use a single static memory group for a single probed unit virtio-mem: use a single dynamic memory group for a single virtio-mem device mm/memory_hotplug: memory group aware "auto-movable" online policy mm/memory_hotplug: improved dynamic memory group aware "auto-movable" online policy drivers/acpi/acpi_memhotplug.c | 35 +++- drivers/base/memory.c | 225 ++++++++++++++++++++--- drivers/dax/kmem.c | 40 +++- drivers/virtio/virtio_mem.c | 22 ++- include/linux/memory.h | 55 +++++- include/linux/memory_hotplug.h | 21 ++- include/linux/mmzone.h | 7 + mm/memory_hotplug.c | 325 ++++++++++++++++++++++++++++++++- mm/page_alloc.c | 3 + 9 files changed, 683 insertions(+), 50 deletions(-)