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dom0 hangs when rebooting debian lenny domU
by Günter Zimmermann 25 Nov '09

25 Nov '09

Dear all, I have a reproducible issue with centos54 dom0 and debian lenny domU using pygrub. As far as I enter "shutdown -r now" in the running Debian Lenny DomU the whole system hangs. Keyboard is dead, network is dead and no more logging. Ending up in a hardware reset of the box. I was able to reproduce this 3 times. Restarting with xm reboot debian50 works without problems. Is there a possibility to debug this behavior? Unfortunately I neither had any logging in /var/log/* nor in /var/log/xen/* or on console. The debian lenny installation was done using debootsrap. No additional software has been installed in the debian domain. This is my cfg file for the Debian Lenny domain: bootloader = "/usr/bin/pygrub" memory = 1024 extra = "3" name = "debian50" vcpus = 1 vif = [ 'bridge=xenbr1' ] disk = [ 'phy:store/debian50_boot,xvda,w', 'phy:store/debian50_root,xvdb,w', 'phy:store/debian50_usr,xvdc,w', 'phy:store/debian50_var,xvdd,w', 'phy:store/debian50_tmp,xvde,w', 'phy:store/debian50_home,xvdf,w', 'phy:store/debian50_swap,xvdg,w', 'phy:store/compile,xvdh,w'] hostname = "debian50.zimmermann.com" on_poweroff = 'destroy' on_reboot = 'restart' on_crash = 'restart' pci = [ '0000:09:04.0' ] Best Regards, Günter Zimmermann

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Unknown boot option `pciback.hide=(09:04.0)': ignoring
by Günter Zimmermann 25 Nov '09

25 Nov '09

Good morning, I need to use pciback.hide to hide a pci card because I want to pci passthrough that card to a domU. My hardware neither supports Intel-Vt-d nor AMD's IOMMU. Unfortunately this doesn't seem to work in Centos 54 anymore. I guess it doesn't work because it is not compiled into the kernel, but as a module. I got the following error in dmesg and the pci device is still listed in dom0 in lspci. Bootdata ok (command line is ro root=/dev/dom0/root pciback.hide=(09:04.0)) Kernel command line: ro root=/dev/dom0/root pciback.hide=(09:04.0) Unknown boot option `pciback.hide=(09:04.0)': ignoring I also tried to update initrd to include the module but got the same error message as above. mkinitrd --with=pciback /boot/initrd-2.6.18-164.6.1.el5xen_pcipt 2.6.18-164.6.1.el5xen title CentOS (2.6.18-164.6.1.el5xen PCI PT) root (hd1,0) kernel /xen.gz-2.6.18-164.6.1.el5 module /vmlinuz-2.6.18-164.6.1.el5xen ro root=/dev/dom0/root pciback.hide=(09:04.0) module /boot/initrd-2.6.18-164.6.1.el5xen_pcipt Is there any option to use pciback.hide kernel parameter without compiling a custom kernel? Thanks in advance Günter Zimmermann

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virt-manager issues?
by Dennis J. 24 Nov '09

24 Nov '09

Hi, A short while ago I renamed two VMs by shutting them down, lvrenaming the storage devices and adjusting the storage path and vm name using "virsh edit". This works fine so far and "virsh list" shows them correctly however virt-manager has gone bonkers and still shows them with the old names and alternating between the status "Shutoff" and "Running" with every display refresh and CPU usage alternating between 0% and 100%. All other VMs on the host are fine and are displayed correctly by virt-manager. Does anybody know what the problem could be and how to fix it? While this issue seems to display related rather than being an actual problem with the VMs it's pretty irritating to say the least. Regards, Dennis

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Endless reboot of Solaris 10 under KVM
by Mathieu Baudier 21 Nov '09

21 Nov '09

Hi, in order to test a future deployment of our apps on Solaris, I tried to virtualize Solaris 10 (update 7) in KVM. It installed fine but afterward it keep rebooting: reboot -> GRUB -> reboot -> GRUB etc. I know that Solaris is not officially supported by CentOS/KVM in CentOS 5.4: http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5.4/html/Virtuali… And the issue seems to be well known: http://www.linuxquestions.org/questions/linux-software-2/solaris-10-guest-e… I got Solaris to work virtualized in VirtualBox 3.0.x (in Fedora) so I have a workaround. So, I don't have much hope that one can get Solaris to work under KVM, but I still wanted to ask here, in case some of you would have faced this already and would know some magic trick... (or at least to spread the information) Cheers, Mathieu

1 0

steadily increasing/high loadavg without i/o wait or cpu utilization
by Günter Zimmermann 20 Nov '09

20 Nov '09

Hi all, I just installed centos 5.4 xen-kernel on intel core i5 machine as dom0. After some hours of syncing a raid10 array (8 sata disk) I noticed a steadily increasing loadavg. I think without reasonable i/o wait or cpu utilization the loadavg on this system should be very lower. If this loadavg is normal I would be greatful if somone could explain why. The screenshots below show that there is neither much i/o wait nor much cpu utilization. top - 09:10:25 up 9:26, 1 user, load average: 7.24, 7.63, 7.72 Tasks: 116 total, 4 running, 112 sleeping, 0 stopped, 0 zombie Cpu0 : 0.0%us, 42.5%sy, 0.0%ni, 57.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu1 : 0.0%us, 1.3%sy, 0.0%ni, 97.7%id, 0.0%wa, 0.0%hi, 0.0%si, 1.0%st Cpu2 : 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Cpu3 : 0.0%us, 10.0%sy, 0.0%ni, 89.0%id, 0.0%wa, 0.0%hi, 0.0%si, 1.0%st Mem: 7805952k total, 809612k used, 6996340k free, 112092k buffers Swap: 0k total, 0k used, 0k free, 341304k cached [root@vserver ~]# iostat -d -x sda sdb sdc sdd sde sdf sg sdh Linux 2.6.18-164.6.1.el5xen (vserver.zimmermann.com) 20.11.2009 Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 1364,57 0,66 1820,12 0,89 25477,44 12,37 14,00 1,11 0,61 0,41 75,10 sdb 1167,12 0,68 2017,45 0,89 25476,53 12,47 12,63 1,16 0,57 0,39 79,49 sdc 1308,06 0,66 1876,65 0,91 25477,64 12,50 13,58 1,14 0,61 0,42 78,73 sdd 1267,27 0,66 1917,28 0,92 25476,32 12,57 13,29 1,09 0,57 0,42 80,16 sde 1146,76 0,63 2037,99 0,87 25477,94 11,96 12,50 0,98 0,48 0,31 63,80 sdf 1126,88 0,64 2057,62 0,87 25475,99 12,02 12,38 1,08 0,52 0,34 69,89 sdh 472,21 0,66 2712,31 0,92 25476,13 12,43 9,39 0,66 0,24 0,15 41,03 [root@vserver ~]# cat /proc/loadavg 7.22 7.58 7.69 8/129 23348 Best regards, Günter Zimmermann

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Re: [CentOS-virt] steadily increasing/high loadavg without i/o wait or cpu utilization
by Christopher G. Stach II 20 Nov '09

20 Nov '09

----- "Günter Zimmermann" <guenter.zimmermann(a)gmx.at> wrote: > Thank you for your reply. I could find just one process in D and this > is > a delayed resync from another raid device. It is delayed because of > the > big resync in progress. I think this is not the problem. Could the > running resync cause the high loadavg without showing up i/o wait or > cpu > utilization in top? It sure can. All of the D, R, and Zs count toward your load average. It looks like you should be somewhere approaching 8. -- Christopher G. Stach II

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Xen domU default gateway missing/ARP table full
by Ken Bass 20 Nov '09

20 Nov '09

I have been trying to figure out why my domU NIC becomes unreachable (could not even ping) at various times. (Normally when the server was trying to update clamav from the various busy mirrors at 4am). There also seemed to be some latency when connecting which I chalked up to it being a virtual machine. When I checked my logs, I found thousands of : Nov 17 04:07:52 nomad kernel: Neighbour table overflow. and applications reporting errors such as: Nov 17 04:08:05 nomad freshclam[4085]: nonblock_connect: connect(): fd=5 errno=105: No buffer space available I am running a routed (not bridged) configuration. What I figured out is that each Centos 5.4 domU is maintaining an ARP table. That table is filling up which causes the network to be unreachable until entries are purged from the cache. Since this is a routed configuration, the ARP table should really only consist of two or three entries, my domU, my dom0, and the gateway. It appears the networking-scripts until Centos are ignoring the GATEWAY entry. I end up with route of: 169.254.0.0 * 255.255.0.0 U 0 0 0 eth0 default * 0.0.0.0 U 0 0 0 eth0 The default route should be the specific IP address in my /etc/sysconfig/network file. When I manually add the route, the arp table issue is fixed. The network stack no longer trys to query an arp entry for every IP address. I found this bug at Xen which was closed as INVALID saying 'Centos is broken'. That was from 2006. http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=596 Any ideas on what is broken and what the correct fix is? Right now, I just added /sbin/route add -net 0.0.0.0 netmask 0.0.0.0 gw x.x.x.x to my /etc/rc.local which seems like a hack solution.

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Re: [CentOS-virt] steadily increasing/high loadavg without i/o wait or cpu utilization
by Christopher G. Stach II 20 Nov '09

20 Nov '09

----- "Günter Zimmermann" <guenter.zimmermann(a)gmx.at> wrote: > Hi all, > > I just installed centos 5.4 xen-kernel on intel core i5 machine as > dom0. > After some hours of syncing a raid10 array (8 sata disk) I noticed a > steadily increasing loadavg. I think without reasonable i/o wait or > cpu > utilization the loadavg on this system should be very lower. If this > loadavg is normal I would be greatful if somone could explain why. > The > screenshots below show that there is neither much i/o wait nor much > cpu > utilization. Do you have any zombie or D state processes? Try: ps -eo stat,command | awk '$1 ~ /^[DRZ]/{print}' If you have any in D, you can use SysRq-T and/or the pid's wchan in /proc to figure out what they're doing or dmesg to figure out where they may have barfed. -- Christopher G. Stach II

2 1

xen host system capacity utilization
by Dennis J. 18 Nov '09

18 Nov '09

Hi, I'm wondering what the proper way is to determine the utilization of host resources when running a couple of VMs. I know xentop but the man-page isn't exactly helpful in explaining what the values it displays actually mean. What I'm looking for is a way to say "Ok, i have 4 VM's running and right now they utilize 40% of the cpu resources the host has, 50% of disk i/o and 30% of network i/o" so that I can determine if and how many additional VMs I can run on this machine? What is the proper way to accomplish this? Regards, Dennis

1 0

High CPU usage when running a CentOS guest in VirtualBox
by Sagi Bashari 16 Nov '09

16 Nov '09

Hi, I am running CentOS 5.3 32bit as a VirtualBox 3.0.0 guest running on Windows XP. The Windows host CPU usage is constantly at 50% although the CentOS guest is completely idle (i.e. 0.00 load average). I know this is a common problem related to the 1000Hz frequency that the CentOS kernel runs at. With previous versions of CentOS, I used the kernel-vm package [1] and it solved my problem. However, according to the README [2] this isn't necessary as of CentOS 5.3 and therefore these packages are not maintained anymore (the latest released kernel-vm is 2.6.18-92.1.22). >From what I understand, as of CentOS 5.3 it is possible to use the "divider=10 clocksource=acpi_pm" to reduce the frequency to 100Hz. I tried this setting, and it made no difference at all. I also tried to install the VirtualBox guest extensions, and still, the host CPU never goes below 50%. Is there any way to solve this issue without resorting to a custom kernel build? Thanks, Sagi [1] http://people.centos.org/tru/kernel-vm/ [2] http://people.centos.org/tru/kernel-vm/readme.txt

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