Re: Regression in vga performance between 0.11.1 and 0.12.1.1

[Adam Greenblatt <adam.greenblatt@gmail.com>]

Avi,
   Sure -- you can download a tarball of kvm_stat logfiles from:

http://misc.cyclecounters.org/qemu-logs.tgz

I ran three workloads (a short, medium, and long) against both
0.11.1 and 0.12.3.  Each workload was started with:

time ~/qemu-0.12.3/bin/qemu-system-x86_64 -m 1536 -soundhw es1370 -smp 4 
-usb -usbdevice tablet -vga std -cpu core2duo -snapshot -name "VKoala 
(r/o)",process="VKoala" -net nic,macaddr=DE:AD:BE:EF:00:08 -net 
tap,vlan=0,ifname=tap6,script=no,downscript=no /vm/ubuntu-9.10/0008.img

(or ~/qemu-0.11.1/bin/... and the same options.)

For the "short" workload, I just shut down the Ubuntu guest immediately 
after
it finishes logging me in.

For the "medium" workload, I open up an 80x43 terminal window in the guest,
and execute:

yes 1234567890123456789012345678901234567890 | head -n 10000

before shutting down the guest.  For the "long" workload, I open up the
same terminal window and execute:

yes 1234567890123456789012345678901234567890 | head -n 100000

before shutting down the guest.

When running these workloads under 0.12.3, you can watch the screen redraw;
it takes 1 or 2 seconds just to put up the desktop background after the 
splash screen.
Top shows the `VKoala' process as pegging one or more cpus, while the host's
X server is essentially idle (< 5% of a cpu).

When running these workloads under 0.11.1, the screen redraw is too fast to
notice -- it appears to just "blink" up instantly.  Top shows the `VKoala'
process as pegging one or more cpus during boot.  When the terminal is busy,
top shows `VKoala' and the host's X server both using ~60% of a cpu -- 
so the
guest is probably being somewhat limited by the host's wimpy graphics.

Hope this is the info you needed.  Thanks for your help!  Aloha,
   Adam

Avi Kivity wrote:
> On 04/28/2010 10:33 PM, Adam Greenblatt wrote:
>> Hi,
>>   I noticed that certain guests (for example, Ubuntu 9.04, Ubuntu 9.10,
>> and the Ubuntu 10.04 release candidate) show dramatically (~100x) slower
>> graphical output when running under qemu-kvm-0.12.1.1 than under 
>> qemu-kvm-0.11.1.
>> Other guests, notably Windows XP and Windows Vista, run fine under both
>> version of qemu.  The regression is still present in qemu-kvm-0.12.3.
>
>
> Please post kvm_stat output for the fast and slow cases (preferably 
> running the same workload, perhaps a web page displaying an animation).
>