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#1 2009-04-09 07:47:44

mikber
Member
Registered: 2007-01-29
Posts: 7

What's up with Qemu?

Hi Arch lovers! big_smile

I've been testing out kvm-enabled Qemu since a couple of weeks ago (windows XP guest).
It has been working fine using "qemu-kvm" (qemu 0.9.1) with good performance and nearly no cpu-usage in idle mode. However now with Qemu 0.10.2 using "qemu -enable-kvm" the performance is bad and cpu-usage when idle is around 50% from one of the core's?!
Also before, using -vga std, in windows xp guest I could use a variety of resolution settings (for example 1280x800) now there's only 5 left (800x600,1024x768,1152x864,1280x1024 and 1600x1200)?
Using kernel26 2.6.29.1-3 btw.

What is happening?

Last edited by mikber (2009-04-09 07:49:43)

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#2 2009-04-09 19:22:50

edubarr
Member
Registered: 2009-03-25
Posts: 19

Re: What's up with Qemu?

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#3 2009-04-11 10:45:52

mikber
Member
Registered: 2007-01-29
Posts: 7

Re: What's up with Qemu?

Nope, that was already seen to (chgrp kvm /dev/kvm). It just worked much better before, and the upgrade to latest today made no difference in performance. From version 0.10 the guest windows show a pentium II processor, with 0.9 it was shown as a Qemu 0.9.x -processor...

Last edited by mikber (2009-04-11 10:46:24)

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#4 2009-04-12 00:16:39

tony5429
Member
Registered: 2006-03-28
Posts: 910
Website

Re: What's up with Qemu?

I noticed this issue too. For me, I discovered that I was no longer in the kvm group for some reason...

more /etc/group | grep kvm

I just solved the issue by adding myself back to the group and rebooting,

su
gpasswd -a (username) kvm
reboot

The very odd thing is that I am 99.9% sure I was in the group a couple days ago, and I don't know how or why I was removed.

Last edited by tony5429 (2009-04-12 00:17:04)


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#5 2009-04-12 07:46:55

moljac024
Member
From: Serbia
Registered: 2008-01-29
Posts: 2,676

Re: What's up with Qemu?

tony5429 wrote:

I noticed this issue too. For me, I discovered that I was no longer in the kvm group for some reason...

more /etc/group | grep kvm

I just solved the issue by adding myself back to the group and rebooting,

su
gpasswd -a (username) kvm
reboot

The very odd thing is that I am 99.9% sure I was in the group a couple days ago, and I don't know how or why I was removed.

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#6 2009-04-12 16:47:25

mikber
Member
Registered: 2007-01-29
Posts: 7

Re: What's up with Qemu?

Yeah, well I noticed that too when I got permission problems when accessing /dev/kvm. However I added myself to the kvm group directly... So that's not the problem...

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#7 2009-04-13 03:43:56

_lunix_
Member
From: Sydney Australia
Registered: 2008-10-31
Posts: 17
Website

Re: What's up with Qemu?

I am too noticing high CPU usage with the latest kvm.
I have upgraded to testing and qemu-system-x86_64 sits at 100% cpu constantly, even when the guest is idle.
This is causing the hosts CPU to get quite hot.
I don't want to lodge a bug report if its such an isolated problem but if a few more people come here with the problem then I will post a bug report.

qemu 0.10.2-3

Linux godzilla 2.6.29-ARCH #1 SMP PREEMPT Wed Apr 8 12:39:28 CEST 2009 x86_64 Intel(R) Core(TM)2 Duo CPU T7500 @ 2.20GHz GenuineIntel GNU/Linux

[lunix@godzilla ~]$ acpitool
  Battery #1     : charged, 100.0%, -691:00:00
  AC adapter     : on-line
  Thermal zone 1 : ok, 62 C

/usr/bin/qemu-system-x86_64  -enable-kvm \
                                                       -name puppetmaster \
                                                       -smp 1 \
                                                       -m 512 \
                                                       -vnc :1 \
                                                       -daemonize \
                                                       -localtime \
                                                       -usb \
                                                       -usbdevice tablet \
                                                       -net nic,macaddr=00:11:2d:02:00:01,model=e1000,vlan=0 \
                                                       -net tap,vlan=0,fd=3 \
                                                       -pidfile /home/vmuser/run/puppetmaster.pid \
                                                       -boot c \
                                                       -drive index=0,media=disk,if=ide,file=/home/vmuser/vdisks/puppetmaster/disk1.img \
                                                       -drive index=1,media=disk,if=ide,file=/home/vmuser/vdisks/puppetmaster/swap.img \
                                                       -drive index=2,media=cdrom,if=ide,file=/home/vmuser/iso/CentOS-5.2-x86_64-bin-DVD.iso

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#8 2009-04-13 05:33:06

_lunix_
Member
From: Sydney Australia
Registered: 2008-10-31
Posts: 17
Website

Re: What's up with Qemu?

More info.........
I noticed there is a KVM PKGBUILD in ABS that builds a standalone kvm-84 package.
I removed qemu 0.10.2-3 and built the KVM-84 pkg from abs.
This fixes the excessive 'sys_timer_settime' problem causing 100%CPU.
Everything works like it used to as long as you don't want to use VDE !!
I can no longer use VDE for networking. *sigh*

No I am a little confused as to where the bug might be.
Is it an upstream ( qemu / kvm )  or Archlinux bug ?
If it was an upstream bug in KVM-84 then wouldn't I see problems with both packages on Archlinux ?

Cheers

Mick
_lunix_

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#9 2009-04-13 08:46:19

voidzero
Member
Registered: 2007-06-21
Posts: 108

Re: What's up with Qemu?

I don't experience these problems. However I also recompiled kernel26 to remove preempt, and change cpu to core2, and timer to 100ms.
Then I recompiled kqemu. It's now working like it should. No 100% cpu.

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#10 2009-04-13 10:16:47

bender02
Member
From: Germany
Registered: 2007-02-04
Posts: 1,328

Re: What's up with Qemu?

voidzero wrote:

I don't experience these problems. However I also recompiled kernel26 to remove preempt, and change cpu to core2, and timer to 100ms.
Then I recompiled kqemu. It's now working like it should. No 100% cpu.

kqemu and kvm are totally different.

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#11 2009-04-13 11:07:58

voidzero
Member
Registered: 2007-06-21
Posts: 108

Re: What's up with Qemu?

And they don't even need eachother?

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#12 2009-04-13 11:11:22

bender02
Member
From: Germany
Registered: 2007-02-04
Posts: 1,328

Re: What's up with Qemu?

voidzero wrote:

And they don't even need eachother?

Nope.

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#13 2009-04-13 14:53:32

mikber
Member
Registered: 2007-01-29
Posts: 7

Re: What's up with Qemu?

_lunix_ are you running win xp -guest? Running with or without kvm enabled for me doesn't give much of a difference in performance. The guest reports the cpu as a pentium II in both cases. Compared qemu with my fedora server which has version 0.9.1 . It's fast (guest xp)! And guest reports cpu as qemu 0.9.1 processor.

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#14 2009-05-04 23:41:29

_lunix_
Member
From: Sydney Australia
Registered: 2008-10-31
Posts: 17
Website

Re: What's up with Qemu?

Sorry I wasn't clear about the guest I was running.
It's CentOS Linux.
I wonder if this is to do with the PREEMPT kernel ?
I will re-compile the kernel today to find out and let everyone know how I go.

Last edited by _lunix_ (2009-05-05 00:27:15)

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#15 2009-05-05 05:42:24

_lunix_
Member
From: Sydney Australia
Registered: 2008-10-31
Posts: 17
Website

Re: What's up with Qemu?

F I X E D  !!!!!!!
I recompiled the kernel using ABS without the tickless stuff and without PREEMPT and all is fixed.
I can now run guests without the high CPU usage/lockups

Last edited by _lunix_ (2009-05-05 07:46:33)

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