High Load / Performance / Solution

[macday]

Hi guys,

tonight I "accidentally" found a solution for possible high load, clock skew, and/or perfomance problems for all my Proxmox Systems (mostly Dell).

Add "clocksource=hpet" to your kernel(s) in your /boot/grub/menu.lst

I thinks this helps all hpet-supported Systems.

Perhaps this could be default in the nexts versions.

Good night.
macday

 

[dietmar]

Perhaps this could be default in the nexts versions.

Is there any documentation about that? Why does it help?

 

[macday]

I am search for a documentation, too. Here ist one in german http://tinyurl.com/2wdokly. I´m in virtualisation since 5 years and I always had problems with the tsc (e.g. vmware server 2.0). Yesterday I installed the Maverick RC and wondered why the maverick-kernel has this option (clocksource=hpet) set as default. So I tried this on my proxmox hosts and my whole system with 10-20 kvms feels much more snappier and the timing problem on one centos-vm(older kernel) is gone. I think the main benefit is the timing is offloaded from the cpu to the hpet chipset. But this may depend on the underlying hardware.

 

[dietmar]

I am search for a documentation, too. Here ist one in german http://tinyurl.com/2wdokly.

The say 'try hpet with AMD- and tsc with Intel-CPUs' - Do you run AMD?

 

[macday]

No I have one Intel Xeon QuadCore in one machine an 2x Intel Nehalems 6 Core Cpus in the other machine.

 

[typo3usa]

Awesome - I will give it a shot later today and report back
we use both amd and intel so will test on both - with of course the variations needed

need to schedule the outage however for the reboots ;-)

 

[linuxdatacenter]

Here's what proxmox reccomends:

http://forum.proxmox.com/threads/2381-Recommended-clock-source-for-KVM-guests
and some notes from fedora:
http://docs.fedoraproject.org/en-US...rtualization-KVM_guest_timing_management.html

in general, what comes out of all the docs I've found is to avoid tsc as the clocksource. The rest is mystery ;-)

 

[macday]

yes, this is for guests only. I tweaked the host.

Here's what proxmox reccomends:

http://forum.proxmox.com/threads/2381-Recommended-clock-source-for-KVM-guests
and some notes from fedora:
http://docs.fedoraproject.org/en-US...rtualization-KVM_guest_timing_management.html

in general, what comes out of all the docs I've found is to avoid tsc as the clocksource. The rest is mystery ;-)