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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 8BF14C433DF for ; Fri, 31 Jul 2020 09:18:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 608F022CAD for ; Fri, 31 Jul 2020 09:18:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FiVCuRWJ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732082AbgGaJSy (ORCPT ); Fri, 31 Jul 2020 05:18:54 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:53500 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1732014AbgGaJSx (ORCPT ); Fri, 31 Jul 2020 05:18:53 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1596187132; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=7KJjJxh3LrCrOmiVZX7zoQLv4kMydPtkCS0ZPjF2DUk=; b=FiVCuRWJSMGZ4b9rF+wVB+oQueeP82nv2MDSJXC97CSYubtzlZHiU4XN51U+MCOWqScXy8 mOJ5H3TdGy9NiTd9bNPGBy6/T2Pi1zPyT9nihh7T1WgqSXEDzxIznsR0G+aUURlfjq5x2+ Z2D/MUYHNS4JWwHc9/lynTjt6YU/6eY= 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-70-SolxhgZkNXO5E6nSxUQ3oA-1; Fri, 31 Jul 2020 05:18:49 -0400 X-MC-Unique: SolxhgZkNXO5E6nSxUQ3oA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 07FF759; Fri, 31 Jul 2020 09:18:47 +0000 (UTC) Received: from t480s.redhat.com (ovpn-113-22.ams2.redhat.com [10.36.113.22]) by smtp.corp.redhat.com (Postfix) with ESMTP id BC0631A835; Fri, 31 Jul 2020 09:18:39 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: virtualization@lists.linux-foundation.org, linux-mm@kvack.org, linux-hyperv@vger.kernel.org, xen-devel@lists.xenproject.org, David Hildenbrand , Andrew Morton , Ard Biesheuvel , Boris Ostrovsky , Dan Williams , Haiyang Zhang , Jason Gunthorpe , Juergen Gross , Julien Grall , Kees Cook , "K. Y. Srinivasan" , Michal Hocko , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= , Stefano Stabellini , Stephen Hemminger , Thomas Gleixner , Wei Liu , Wei Yang Subject: [PATCH RFCv1 0/5] mm/memory_hotplug: selective merging of memory resources Date: Fri, 31 Jul 2020 11:18:33 +0200 Message-Id: <20200731091838.7490-1-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Sender: linux-hyperv-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org Some add_memory*() users add memory in small, contiguous memory blocks. Examples include virtio-mem, hyper-v balloon, and the XEN balloon. This can quickly result in a lot of memory resources, whereby the actual resource boundaries are not of interest (e.g., it might be relevant for DIMMs, exposed via /proc/iomem to user space). We really want to merge added resources in this scenario where possible. Resources are effectively stored in a list-based tree. Having a lot of resources not only wastes memory, it also makes traversing that tree more expensive, and makes /proc/iomem explode in size (e.g., requiring kexec-tools to manually merge resources when creating a kdump header. The current kexec-tools resource count limit does not allow more than ~100GB of memory with a memory block size of 128MB on x86-64). Let's allow to selectively merge resources, speciyfing a parent node and a resource idendifier string. The memory unplug path will properly split up merged resources again. Patch #3 contains a /proc/iomem example. Only tested with virtio-mem. Note: This gets the job done and is comparably simple. More complicated approaches would require introducing IORESOURCE_MERGEABLE and extending our add_memory*() interfaces with a flag, specifying that merging after adding succeeded is acceptable. I'd like to avoid that complexity and code churn for now. David Hildenbrand (5): kernel/resource: make release_mem_region_adjustable() never fail kernel/resource: merge_child_mem_resources() to merge memory resources after adding succeeded virtio-mem: try to merge "System RAM (virtio_mem)" resources xen/balloon: try to merge "System RAM" resources hv_balloon:: try to merge "System RAM" resources drivers/hv/hv_balloon.c | 3 ++ drivers/virtio/virtio_mem.c | 14 ++++- drivers/xen/balloon.c | 4 ++ include/linux/ioport.h | 7 ++- kernel/resource.c | 105 ++++++++++++++++++++++++++++-------- mm/memory_hotplug.c | 22 +------- 6 files changed, 109 insertions(+), 46 deletions(-) -- 2.26.2