Red Hat Bugzilla – Bug 589447
F13 guest X performance when -vga std far slower than CentOS 5.4 guest.
Last modified: 2013-01-09 06:34:13 EST
Created attachment 411863 [details]
F13/i686 guest running under a F12/x86_64 host.
X performance under F13 is around 1/10 of the performance of a CentOS 5.4 guest using the same xorg.conf configuration file.
Host: Fedora 12/x86_64.
Guest: Fedora 13/i686 (2GB, 2CPUs).
Hardware: 2 x Xeon L5530, 12GB, 9800GTX/512MB, nVidia proprietary driver.
$ rpm -qa | grep qemu
Guest command line:
qemu-kvm -cdrom /dev/sr0 -serial telnet::9006,server,nowait -soundhw es1370
-net nic,vlan=1,macaddr=00:E0:81:B0:FB:06,model=e1000 -net
tap,vlan=1,ifname=tap60 -net nic,vlan=2,macaddr=00:E0:81:B0:FB:16,model=e1000
-net tap,vlan=2,ifname=tap61-m2048 -name Fedora-i386-F13 -hda
/usr/drives/kvm/Fedora-i386/Fedora-i386-F13.img -smp2 -usb -usbdevice tablet
-vga std -vnc :6 -boot c
I have an F13 host running an F13 guest that exhibits this problem.
The same host running a Windows XP guest does not exhibit the problem.
There's an upstream discussion that may be related:
I doubt it.
The kerneltrap threads talks about regression between different versions of qemu.
I'm talking about performance regression between different versions of Linux running as guests.
Most likely this is a Fedora X.org issue, and not qemu issue. (If it was a qemu issue, I should have seen the same performance under CentOS and Fedora guests)
Indeed, the qemu issue seems to be SDL changes. This guest is not using SDL, though I am curious why you chose -vga std instead of -vga cirrus. Cirrus should be the default for F13 guests.
Do things speed up considerably when using -vga cirrus?
Performance is much better with -vga cirrus but that doesn't offer resolutions like 1440x900 that I would very much like to use.
As above, vga std gives far wider selection of resolutions (Which I require).
Created attachment 419477 [details]
Xorg.0.log from Rawhide guest
Here's an Xorg.0.log from a similar attempt I made to use -vga std with a Rawhide guest. It worked so well with a CentOS 5.5 guest that I got all excited. :-)
I also tried to use -std vga with a Ubuntu 10.04 guest. It was very slow, too. Its Xorg.0.log does not have the RandR failure or the "EQ overflowing" message that appear in the Rawhide log.
Probably unrelated, but I'd better mention it just in case: in every guest where I've tried -vga std so far (CentOS 5.5, Rawhide, and Ubuntu 10.04), there is a column about 10 pixels wide on the right hand side of the display that appears to contain mangled bits from other parts of the display. I've done 1400x1050 in all 3, no other resolutions tried yet.
I see a similar regression in performance between F13 guest (slow) and RHEL6beta guest (fast) on F13 host even with the cirrus vga.
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