Re: Guest performance is reduced after live migration

[Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>]

Shouta,

Can it be reproduced if thp/hugetlbfs is disabled on both source and destination?

On 11/01/2012 08:12 AM, Shouta.Uehara@jp.yokogawa.com wrote:
> Hello.
> 
> I have a problem with the performance of the guest Linux after live migration.
> When I analyze the file I/O latency of the guest using LMbench3, the latency of
> the guest on the destination host is about 2 times bigger than the guest on the
> source host. As a result that I investigated it, this problem occurs if three
> following conditions are right.
> 
>   1. Use the kernel version 2.6.38.6-26.fc15.x86_64 or later.
>   2. Execute system calls for low level file I/O (read, write, open etc.) on the
>      guest.
>   3. Enable EPT.
> 
> Performance cannot decrease on other tests of LMbench3; numerical operation,
> context switching, memory latencies etc.
> 
> Is this an existing problem ? What should I do to resolve it ?
> 
> ---
> The situation the problem occurs
> 
> CPU models     : Intel Xeon E3-1245 (Both hosts have same cpu.)
> Host kernel    : 3.6.4
> Host OS        : Fedora 16 64bit ver. (Both hosts have same OS.)
> Guest OS       : Fedora 16 64bit ver., kernel 3.1.0-7.fc16.x86_64
> QEMU version   : qemu-kvm 1.2.0
> QEMU parameter : qemu-kvm -m 1024 -drive file=guest.qcow2,if=virtio \
>                  -boot order=c,menu=on -k ja
>                  (-incoming tcp:192.168.0.51:4444   set only destination)
> QEMU command   : migrate -d tcp:192.168.0.51:4444
> Analyses       : LMbench version 3
> 
>         [Guest on the source host]
>         $ ./lat_syscall open
>           Simple open/close: 1.4281 microseconds
>         $ ./lat_syscall read
>           Simple read: 0.1416 microseconds
>         $ ./lat_syscall write
>           Simple write: 0.1194 microseconds
>         $ ./lat_fs -s 0
>           0k      550     98726   247712
>           1k      383     69751   193985
>           4k      381     69348   193383
>           10k     313     54369   155697
> 
>         [Guest on the source host]
>         $ ./lat_syscall open
>           Simple open/close: 1.6126 microseconds
>         $ ./lat_syscall read
>           Simple read: 0.2206 microseconds
>         $ ./lat_syscall write
>           Simple write: 0.1980 microseconds
>         $ ./lat_fs -s 0
>           0k      427     83252   243222
>           1k      315     60530   191650
>           4k      184     34535   190947
>           10k     65      11922   152608
> ---
> 
> Thanks.
> 
>         Shota Uehara <Shouta.Uehara()jp.yokogawa.com>
> 
> 
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