From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42685) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XkDv0-0003aK-Vz for qemu-devel@nongnu.org; Fri, 31 Oct 2014 11:16:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Xk539-0005ha-5L for qemu-devel@nongnu.org; Fri, 31 Oct 2014 01:47:08 -0400 Received: from mga09.intel.com ([134.134.136.24]:9865) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xk538-0005gD-Vk for qemu-devel@nongnu.org; Fri, 31 Oct 2014 01:47:03 -0400 From: Liliang Date: Fri, 31 Oct 2014 13:40:28 +0800 Message-Id: <1414734028-16045-1-git-send-email-liangx.z.li@intel.com> Subject: [Qemu-devel] [PATCH 2/2] docs: Add a document about multiple compression threads List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Li Liang , armbru@redhat.com, lcapitulino@redhat.com From: Li Liang Give some details about how to use the multiple compress threads feature in live migration. Signed-off-by: Li Liang --- docs/multiple-compression-threads.txt | 57 +++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 docs/multiple-compression-threads.txt diff --git a/docs/multiple-compression-threads.txt b/docs/multiple-compression-threads.txt new file mode 100644 index 0000000..83e9e5b --- /dev/null +++ b/docs/multiple-compression-threads.txt @@ -0,0 +1,57 @@ +Use multiple compression(decompression) threads in live migration +================================================================= +Instead of sending the guest memory directly, this solution will +compress the ram page before sending, after receiving, the data how to +us 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 migration time can also be reduced about +80% in a typical case. + +The process of compression will consume additional CPU cycles, and the +extra CPU cycles will increase the migration time. In another hand, +the amount of data transferred will reduced, this factor can reduce +the migration time. If the process of the compression is quickly +enough, then the total migration time can be reduced, multiple +compression threads can be used to accelerate the compression process. + +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 compression threads in live migration +============================================================== +Compression of data will consume lot of extra CPU cycles, 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 the +multiple compression threads will be very helpful. If both the CPU and +the network bandwidth are adequate, use multiple compression threads +can still help to reduce the migration time. + + +Usage +====== +1. Verify the destination QEMU version is able to support the multiple +compression threads migration: + {qemu} info_migrate_capablilites + {qemu} ... compress: off ... + +2. Activate compression on the souce: + {qemu} migrate_set_capability compress on + +3. Set the compression thread count on source: + {qemu} migrate_set_compress_threads 10 + +4. Set the compression level on the source: + {qemu} migrate_set_compress_level 1 + +5. Set the decompression thread count on destination: + {qemu} migrate_set_decompress_threads 5 + +6. Start outgoing migration: + {qemu} migrate -d tcp:destination.host:4444 + {qemu} info migrate + Capablilties: ... compress: on + ... -- 1.9.1