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Diffstat (limited to 'qemu/docs/multi-thread-compression.txt')
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diff --git a/qemu/docs/multi-thread-compression.txt b/qemu/docs/multi-thread-compression.txt deleted file mode 100644 index 3d477c3bd..000000000 --- a/qemu/docs/multi-thread-compression.txt +++ /dev/null @@ -1,149 +0,0 @@ -Use multiple thread (de)compression in live migration -===================================================== -Copyright (C) 2015 Intel Corporation -Author: Liang Li <liang.z.li@intel.com> - -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. |