nosmp Xen kernel boot option renders instances >1 vcpu slow

[John N.]

Hi,

Following nicely the Ganeti Install guide (http://docs.ganeti.org/ganeti/2.6/html/install.html) I added the "nosmp" Xen kernel boot option as recommended for Debian:

"Debian
Besides the ballooning change which you need to set in /etc/xen/xend-config.sxp, you need to set the memory and nosmp parameters in the file /boot/grub/menu.lst."

But I noticed as soon as I have a ganeti instance using more than 1 vcpu the instance gets extremely slow (5x slower!) up to the point that it is nearly unusable. Removing "nosmp" fixes this issue for me. Also I found out that this "nosmp" option is a sort of unsupported configuration (reference: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=637308) and should not be used. Instead dom0_max_vcpus should be used.

Thought it might be good for you guys to know and change the documentation. Cost me quite a lot of time tracking this, what I thought to be a  performance problem, down...

Cheers,
John

[Thomas Thrainer]

Hi,

Thanks for pointing that out! I'll update the documentation for 2.7 and remove the reference to "nosmp".

Thanks,

Thomas

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Thomas Thrainer | Software Engineer | thom...@google.com | 

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