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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 A9968C43463 for ; Mon, 21 Sep 2020 09:12:22 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 23BBE20773 for ; Mon, 21 Sep 2020 09:12:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ZReOK4/c" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 23BBE20773 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:50614 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kKHrx-00059E-1V for qemu-devel@archiver.kernel.org; Mon, 21 Sep 2020 05:12:21 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35990) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kKHqV-0004Iw-4h for qemu-devel@nongnu.org; Mon, 21 Sep 2020 05:10:51 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:44247 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kKHqS-0007a8-5X for qemu-devel@nongnu.org; Mon, 21 Sep 2020 05:10:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600679446; 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: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=BaOOIEf2agpARzSo1qTzBXP2bMM63HOdRfG69yv1QR4=; b=ZReOK4/cnyXnWun3VKF+IQkejCe3c3wPzwTPHwQApvs5W6XZMAcaCWGHAVMMoScgjd0j6k Sb9nLVhRrHebsollYxcV4XCxrk81Ux58hUQuDc7KuI7WBUiaJleZp04xvewSYVvsavorVz yHxguJ+L7KKsK36eSVQ26YV6sMSlwi8= 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-217-sBBJBvaaNKK-I7ROkbUBDQ-1; Mon, 21 Sep 2020 05:10:42 -0400 X-MC-Unique: sBBJBvaaNKK-I7ROkbUBDQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3EA40802B70; Mon, 21 Sep 2020 09:10:41 +0000 (UTC) Received: from [10.36.115.48] (ovpn-115-48.ams2.redhat.com [10.36.115.48]) by smtp.corp.redhat.com (Postfix) with ESMTP id 09E3B68D5F; Mon, 21 Sep 2020 09:10:29 +0000 (UTC) Subject: Re: [PATCH 0/3] Hyper-V Dynamic Memory Protocol driver (hv-balloon) To: "Maciej S. Szmigiero" , Paolo Bonzini , Richard Henderson , Eduardo Habkost References: From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63W5Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAjwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat GmbH Message-ID: Date: Mon, 21 Sep 2020 11:10:27 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US Received-SPF: pass client-ip=207.211.31.81; envelope-from=david@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/21 03:43:14 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.501, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Michael S. Tsirkin" , qemu-devel@nongnu.org, Markus Armbruster , Igor Mammedov , Vitaly Kuznetsov , Boris Ostrovsky Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 20.09.20 15:25, Maciej S. Szmigiero wrote: > From: "Maciej S. Szmigiero" > > This series adds a Hyper-V Dynamic Memory Protocol driver (hv-balloon) > and its protocol definitions. > Also included is a driver providing backing devices for memory hot-add > protocols ("haprots"). > > A haprot device works like a virtual DIMM stick: it allows inserting > extra RAM into the guest at run time. > > The main differences from the ACPI-based PC DIMM hotplug are: > * Notifying the guest about the new memory range is not done via ACPI but > via a protocol handler that registers with the haprot framework. > This means that the ACPI DIMM slot limit does not apply. > > * A protocol handler can prevent removal of a haprot device when it is > still in use by setting its "busy" field. > > * A protocol handler can also register an "unplug" callback so it gets > notified when an user decides to remove the haprot device. > This way the protocol handler can inform the guest about this fact and / or > do its own cleanup. > > The hv-balloon driver is like virtio-balloon on steroids: it allows both > changing the guest memory allocation via ballooning and inserting extra > RAM into it by adding haprot virtual DIMM sticks. > One of advantages of these over ACPI-based PC DIMM hotplug is that such > memory can be hotplugged in much smaller granularity because the ACPI DIMM > slot limit does not apply. Reading further below, it's essentially DIMM-based memory hotplug + virtio-balloon - except the 256MB DIMM limit. But reading below, I don't see how you want to avoid the KVM memory slot limit that's in a similar size (I recall 256*2 due to 2 address spaces). Or avoid VMA limits when wanting to grow a VM big in very tiny steps over time (e.g., adding 64MB at a time). > > In contrast with ACPI DIMM hotplug where one can only request to unplug a > whole DIMM stick this driver allows removing memory from guest in single > page (4k) units via ballooning. > Then, once the guest has released the whole memory backed by a haprot > virtual DIMM stick such device is marked "unused" and can be removed from > the VM, if one wants so. > A "HV_BALLOON_HAPROT_UNUSED" QMP event is emitted in this case so the > software controlling QEMU knows that this operation is now possible. > > The haprot devices are also marked unused after a VM reboot (with a > corresponding "HV_BALLOON_HAPROT_UNUSED" QMP event). > They are automatically reinserted (if still present) after the guest > reconnects to this protocol (a "HV_BALLOON_HAPROT_INUSE" QMP event is then > emitted). > > For performance reasons, the guest-released memory is tracked in few range > trees, as a series of (start, count) ranges. > Each time a new page range is inserted into such tree its neighbors are > checked as candidates for possible merging with it. > > Besides performance reasons, the Dynamic Memory protocol itself uses page > ranges as the data structure in its messages, so relevant pages need to be > merged into such ranges anyway. > > One has to be careful when tracking the guest-released pages, since the > guest can maliciously report returning pages outside its current address > space, which later clash with the address range of newly added memory. > Similarly, the guest can report freeing the same page twice. > > The above design results in much better ballooning performance than when > using virtio-balloon with the same guest: 230 GB / minute with this driver > versus 70 GB / minute with virtio-balloon. I assume these numbers apply with Windows guests only. IIRC Linux hv_balloon does not support page migration/compaction, while virtio-balloon does. So you might end up with quite some fragmented memory with hv_balloon in Linux guests - of course, usually only in corner cases. > > During a ballooning operation most of time is spent waiting for the guest > to come up with newly freed page ranges, processing the received ranges on > the host side (in QEMU / KVM) is nearly instantaneous. > > The unballoon operation is also pretty much instantaneous: > thanks to the merging of the ballooned out page ranges 200 GB of memory can > be returned to the guest in about 1 second. > With virtio-balloon this operation takes about 2.5 minutes. > > These tests were done against a Windows Server 2019 guest running on a > Xeon E5-2699, after dirtying the whole memory inside guest before each > balloon operation. > > Using a range tree instead of a bitmap to track the removed memory also > means that the solution scales well with the guest size: even a 1 TB range > takes just few bytes of memory. > Example usage: > * Add "-device vmbus-bridge,id=vmbus-bridge -device hv-balloon,id=hvb" > to the QEMU command line and set "maxmem" value to something large, > like 1T. > > * Use QEMU monitor commands to add a haprot virtual DIMM stick, together > with its memory backend: > object_add memory-backend-ram,id=mem1,size=200G > device_add mem-haprot,id=ha1,memdev=mem1 > The first command is actually the same as for ACPI-based DIMM hotplug. > > * Use the ballooning interface monitor commands to force the guest to give > out as much memory as possible: > balloon 1 At least under virtio-balloon with Linux, that will pretty sure trigger a guest crash. Is something like that expected to work with Windows guests reasonably well? > The ballooning interface monitor commands can also be used to resize > the guest up and down appropriately. > > * One can check the current guest size by issuing a "info balloon" command. > This is useful to know what is happening, since large ballooning or > unballooning operations take some time to complete. So, every time you want to add more memory (after the balloon was deflated) to a guest, you have to plug a new mem-haprot device, correct? So your QEMU user has to be well aware of how to balance "balloon" and "object_add/device_add/object_del_device_del" commands to achieve the desired guest size. > > * Once the guest releases the whole memory backed by a haprot device > (or is restarted) a "HV_BALLOON_HAPROT_UNUSED" QMP event will be > generated. > The haprot device then can be removed, together with its memory backend: > device_del ha1 > object_del mem1 So, you rely on some external entity to properly shrink a guest again (e.g., during reboot). > > Future directions: > * Allow sharing the ballooning QEMU interface between hv-balloon and > virtio-balloon drivers. > Currently, only one of them can be added to the VM at the same time. Yeah, that makes sense. Only one at a time. > > * Allow new haport devices to reuse the same address range as the ones > that were previously deleted via device_del monitor command without > having to restart the VM. > > * Add vmstate / live migration support to the hv-balloon driver. > > * Use haprot device to also add memory via virtio interface (this requires > defining a new operation in virtio-balloon protocol and appropriate > support from the client virtio-balloon driver in the Linux kernel). Most probably not the direction we are going to take. We have virtio-mem for clean, fine-grained, NUMA-aware, paravirtualized memory hot(un)plug now, and we are well aware of various issues with (base-page size based) memory ballooning that are fairly impossible to solve (especially in the context of vfio). -- Thanks, David / dhildenb