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This bug has been copied from bug #690521 and has been proposed to be backported to 5.6 z-stream (EUS).
Reproduced on kvm-83-224.el5. VERIFIED on kvm-83-224.el5_6.1 In order to rule networks' bottleneck out,I migrated to localhost. 1.boot src guest #//usr/libexec/qemu-kvm -rtc-td-hack -usbdevice tablet -no-hpet -drive file=/home/rhel5u6_64.qcow2.2,if=virtio,boot=on,werror=stop,cache=none,format=qcow2,media=disk -cpu qemu64,+sse2 -smp 2 -m 4G -net nic,macaddr=00:12:24:5f:a6:2f,model=virtio,vlan=0 -net tap,script=/etc/qemu-ifup,vlan=0 -uuid `uuidgen` -vnc :2 -boot dc -balloon virtio -monitor unix:/tmp/tt1,server,nowait -notify all -M rhel5.6.0 2./usr/libexec/qemu-kvm -rtc-td-hack -usbdevice tablet -no-hpet -drive file=/home/rhel5u6_64.qcow2.2,if=virtio,boot=on,werror=stop,cache=none,format=qcow2,media=disk -cpu qemu64,+sse2 -smp 2 -m 4G -net nic,macaddr=00:12:24:5f:a6:2f,model=virtio,vlan=0 -net tap,script=/etc/qemu-ifup,vlan=0 -uuid `uuidgen` -vnc :3 -boot dc -balloon virtio -monitor unix:/tmp/tt1,server,nowait -notify all -M rhel5.6.0 -incoming tcp:0:5888 3.in src qemu 3.1 run comment0 program in guest. 3.2 migrate_set_speed 1G 3.3 do migration 3.4 check "info migrate",watch "transferred ram" Results: on kvm-83-224.el5 ,the average speed is 60MB ,max speed could reach reach ~137MBps on kvm-83-224.el5_6.1 ,the average speed is 150MB/s ,max speed could reach 400MB/s Based on above ,speed increased alot ; So this issue has been fixed ald ,move status to VERIFIED.
the comment-0 program should be run at least as many times as the VM has cores, it doesn't really create a load, it just dirties some RAM constantly
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: Due to a regression introduced in Red Hat Enterprise Linux 5.6, duplicate pages may have been transferred during a live migration of a KVM virtual machine. Consequent to this, when a system was under heavy load, such a migration may have failed to complete in some scenarios. This update applies a patch that reverts this regression. As a result, the live migration is now more efficient and no longer fails to complete under heavy load.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHBA-2011-0499.html