From patchwork Thu May 7 16:46:01 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Juan Quintela X-Patchwork-Id: 469733 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 2EB3514028F for ; Fri, 8 May 2015 02:47:05 +1000 (AEST) Received: from localhost ([::1]:52103 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YqOwx-0005nS-60 for incoming@patchwork.ozlabs.org; Thu, 07 May 2015 12:47:03 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48675) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YqOwJ-0004jk-MX for qemu-devel@nongnu.org; Thu, 07 May 2015 12:46:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YqOwH-00059q-7m for qemu-devel@nongnu.org; Thu, 07 May 2015 12:46:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53562) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YqOwH-00059g-0Z for qemu-devel@nongnu.org; Thu, 07 May 2015 12:46:21 -0400 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (Postfix) with ESMTPS id 969EFC658A; Thu, 7 May 2015 16:46:20 +0000 (UTC) Received: from trasno.mitica (ovpn-116-68.ams2.redhat.com [10.36.116.68]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t47GkHGR018088; Thu, 7 May 2015 12:46:19 -0400 From: Juan Quintela To: qemu-devel@nongnu.org Date: Thu, 7 May 2015 18:46:01 +0200 Message-Id: <1431017176-3301-2-git-send-email-quintela@redhat.com> In-Reply-To: <1431017176-3301-1-git-send-email-quintela@redhat.com> References: <1431017176-3301-1-git-send-email-quintela@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Yang Zhang , Liang Li Subject: [Qemu-devel] [PULL 01/16] docs: Add a doc about multiple thread compression X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Liang Li Give some details about the multiple thread (de)compression and how to use it in live migration. Signed-off-by: Liang Li Signed-off-by: Yang Zhang Reviewed-by: Dr.David Alan Gilbert Reviewed-by: Juan Quintela Signed-off-by: Juan Quintela --- docs/multi-thread-compression.txt | 149 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 149 insertions(+) create mode 100644 docs/multi-thread-compression.txt diff --git a/docs/multi-thread-compression.txt b/docs/multi-thread-compression.txt new file mode 100644 index 0000000..3d477c3 --- /dev/null +++ b/docs/multi-thread-compression.txt @@ -0,0 +1,149 @@ +Use multiple thread (de)compression in live migration +===================================================== +Copyright (C) 2015 Intel Corporation +Author: Liang Li + +This work is licensed under the terms of the GNU GPLv2 or later. See +the COPYING file in the top-level directory. + +Contents: +========= +* Introduction +* When to use +* Performance +* Usage +* TODO + +Introduction +============ +Instead of sending the guest memory directly, this solution will +compress the RAM page before sending; after receiving, the data will +be decompressed. Using compression in live migration can help +to reduce the data transferred about 60%, this is very useful when the +bandwidth is limited, and the total migration time can also be reduced +about 70% in a typical case. In addition to this, the VM downtime can be +reduced about 50%. The benefit depends on data's compressibility in VM. + +The process of compression will consume additional CPU cycles, and the +extra CPU cycles will increase the migration time. On the other hand, +the amount of data transferred will decrease; this factor can reduce +the total migration time. If the process of the compression is quick +enough, then the total migration time can be reduced, and multiple +thread compression can be used to accelerate the compression process. + +The decompression speed of Zlib is at least 4 times as quick as +compression, if the source and destination CPU have equal speed, +keeping the compression thread count 4 times the decompression +thread count can avoid resource waste. + +Compression level can be used to control the compression speed and the +compression ratio. High compression ratio will take more time, level 0 +stands for no compression, level 1 stands for the best compression +speed, and level 9 stands for the best compression ratio. Users can +select a level number between 0 and 9. + + +When to use the multiple thread compression in live migration +============================================================= +Compression of data will consume extra CPU cycles; so in a system with +high overhead of CPU, avoid using this feature. When the network +bandwidth is very limited and the CPU resource is adequate, use of +multiple thread compression will be very helpful. If both the CPU and +the network bandwidth are adequate, use of multiple thread compression +can still help to reduce the migration time. + +Performance +=========== +Test environment: + +CPU: Intel(R) Xeon(R) CPU E5-2680 0 @ 2.70GHz +Socket Count: 2 +RAM: 128G +NIC: Intel I350 (10/100/1000Mbps) +Host OS: CentOS 7 64-bit +Guest OS: RHEL 6.5 64-bit +Parameter: qemu-system-x86_64 -enable-kvm -smp 4 -m 4096 + /share/ia32e_rhel6u5.qcow -monitor stdio + +There is no additional application is running on the guest when doing +the test. + + +Speed limit: 1000Gb/s +--------------------------------------------------------------- + | original | compress thread: 8 + | way | decompress thread: 2 + | | compression level: 1 +--------------------------------------------------------------- +total time(msec): | 3333 | 1833 +--------------------------------------------------------------- +downtime(msec): | 100 | 27 +--------------------------------------------------------------- +transferred ram(kB):| 363536 | 107819 +--------------------------------------------------------------- +throughput(mbps): | 893.73 | 482.22 +--------------------------------------------------------------- +total ram(kB): | 4211524 | 4211524 +--------------------------------------------------------------- + +There is an application running on the guest which write random numbers +to RAM block areas periodically. + +Speed limit: 1000Gb/s +--------------------------------------------------------------- + | original | compress thread: 8 + | way | decompress thread: 2 + | | compression level: 1 +--------------------------------------------------------------- +total time(msec): | 37369 | 15989 +--------------------------------------------------------------- +downtime(msec): | 337 | 173 +--------------------------------------------------------------- +transferred ram(kB):| 4274143 | 1699824 +--------------------------------------------------------------- +throughput(mbps): | 936.99 | 870.95 +--------------------------------------------------------------- +total ram(kB): | 4211524 | 4211524 +--------------------------------------------------------------- + +Usage +===== +1. Verify both the source and destination QEMU are able +to support the multiple thread compression migration: + {qemu} info_migrate_capabilities + {qemu} ... compress: off ... + +2. Activate compression on the source: + {qemu} migrate_set_capability compress on + +3. Set the compression thread count on source: + {qemu} migrate_set_parameter compress_threads 12 + +4. Set the compression level on the source: + {qemu} migrate_set_parameter compress_level 1 + +5. Set the decompression thread count on destination: + {qemu} migrate_set_parameter decompress_threads 3 + +6. Start outgoing migration: + {qemu} migrate -d tcp:destination.host:4444 + {qemu} info migrate + Capabilities: ... compress: on + ... + +The following are the default settings: + compress: off + compress_threads: 8 + decompress_threads: 2 + compress_level: 1 (which means best speed) + +So, only the first two steps are required to use the multiple +thread compression in migration. You can do more if the default +settings are not appropriate. + +TODO +==== +Some faster (de)compression method such as LZ4 and Quicklz can help +to reduce the CPU consumption when doing (de)compression. If using +these faster (de)compression method, less (de)compression threads +are needed when doing the migration.