From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33371) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YZyK9-000131-9H for qemu-devel@nongnu.org; Mon, 23 Mar 2015 05:07:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YZyK5-00029K-Ol for qemu-devel@nongnu.org; Mon, 23 Mar 2015 05:07:05 -0400 Received: from mga03.intel.com ([134.134.136.65]:7956) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YZxvV-00029J-Fm for qemu-devel@nongnu.org; Mon, 23 Mar 2015 04:41:37 -0400 From: Liang Li Date: Mon, 23 Mar 2015 16:32:16 +0800 Message-Id: <1427099549-10633-2-git-send-email-liang.z.li@intel.com> In-Reply-To: <1427099549-10633-1-git-send-email-liang.z.li@intel.com> References: <1427099549-10633-1-git-send-email-liang.z.li@intel.com> Subject: [Qemu-devel] [v6 01/14] docs: Add a doc about multiple thread compression List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: quintela@redhat.com, Liang Li , dgilbert@redhat.com, lcapitulino@redhat.com, yang.z.zhang@intel.com, quintela@redhate.com, amit.shah@redhat.com 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 --- 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. -- 1.9.1