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From: | Peter Lieven |
Subject: | Re: [Qemu-devel] [PATCH] migration: use XBZRLE only after bulk stage |
Date: | Fri, 01 Mar 2013 15:50:55 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130221 Thunderbird/17.0.3 |
On 01.03.2013 15:23, Eric Blake wrote:
On 03/01/2013 07:13 AM, Peter Lieven wrote:On 01.03.2013 15:08, Eric Blake wrote:On 03/01/2013 07:06 AM, Peter Lieven wrote:Do you have any benchmark numbers? At any rate, the explanation seems sound, so a benchmark should show this.Do you have a particular test pattern in mind? If there is nothing going on in the VM XBZRLE will not be better than normal copy at all. Otherwise you will have N xbzrle misses and 0 xbzrle pages without the patch and 0 xbzrle misses and 0 xbzrle pages with the patch.How about a migration of a guest running the synthetic r/w load generator in docs/xbzrle.txt?Good idea. I will leave max downtime and bandwidth at default values. Would you be happy with 1GB vRAM and 256MB page cache?Sure - just any run that you can do that shows before and after numbers, and that is described well enough to be a reproducible test. Final statistics on the migration (pages transferred, cache hits and misses, etc) and time spent on the migration will hopefully show an improvement, but most important is that they do not show a regression.
just a quick test on my desktop: ~/git/qemu$ x86_64-softmmu/qemu-system-x86_64 -k de -enable-kvm -m 1024 -drive if=virtio,file=iscsi://172.21.200.31/iqn.2001-05.com.equallogic:0-8a0906-16470e107-713001aa6de511e0-001-test/0 -vnc :1 -boot dc -monitor stdio using ubuntu 12.04.1 desktop and the example from docs/xbzrle.txt a) with the patch (qemu) info migrate capabilities: xbzrle: on Migration status: completed total time: 22185 milliseconds downtime: 29 milliseconds transferred ram: 706034 kbytes remaining ram: 0 kbytes total ram: 1057216 kbytes duplicate: 108556 pages normal: 175146 pages normal bytes: 700584 kbytes cache size: 67108864 bytes xbzrle transferred: 3127 kbytes xbzrle pages: 117811 pages xbzrle cache miss: 18750 xbzrle overflow : 0 b) without the patch (qemu) info migrate capabilities: xbzrle: on Migration status: completed total time: 22410 milliseconds downtime: 21 milliseconds transferred ram: 721318 kbytes remaining ram: 0 kbytes total ram: 1057216 kbytes duplicate: 105553 pages normal: 179589 pages normal bytes: 718356 kbytes cache size: 67108864 bytes xbzrle transferred: 630 kbytes xbzrle pages: 21527 pages xbzrle cache miss: 179589 xbzrle overflow : 0
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