March 12, 2009 Archives

12-03-2009 17:06

CPU Quota and priority for Xen

xm sched-credit -d <domain> lists weight and cap
xm-sched-credit -d <domain> -w <weight> sets the weight
xm-sched-credit -d <domain> -c <cap> sets the cap


Each domain (including Host OS) is assigned a weight and a cap.


A domain with a weight of 512 will get twice as much CPU as a domain with a weight of 256 on a contended host. Legal weights range from 1 to 65535 and the default is 256.


The cap optionally fixes the maximum amount of CPU a domain will be able to consume, even if the host system has idle CPU cycles. The cap is expressed in percentage of one physical CPU: 100 is 1 physical CPU, 50 is half a CPU, 400 is 4 CPUs, etc... The default, 0, means there is no upper cap.

SMP load balancing

The credit scheduler automatically load balances guest VCPUs across all available physical CPUs on an SMP host. The administrator does not need to manually pin VCPUs to load balance the system. However, she can restrict which CPUs a particular VCPU may run on using the generic vcpu-pin interface.

All copied off the xensource wiki

Posted by DaveQB | Permanent Link | Categories: IT

12-03-2009 11:24

GNU Screen - what a wonderful app

Screen is one of the most handy applications out there. I sometimes need to run screen, and in that, ssh to another server and then run or join screen there. I have done this successfully before but never saved how. Here is a nice page that explains 2 tips with regards to this.

...if you ever need to ssh to another machine and run screen there while already in a screen session on the first (i.e., nested screens, if you will), you'll realize that CTRL+A can no longer be used as the 'magic' key for both screen sessions. fortunately, the 'magic' screen key can be changed on a session-by-session basis, and can be set to any reasonable value. for example, using

screen -e^Vv
to start your session will make CTRL-V the 'magic' key.

Posted by DaveQB | Permanent Link | Categories: IT

12-03-2009 11:13

Linux Virtualisation comparison table

A simple table to use to see the difference of all the virtualisation options for Linux.

Posted by DaveQB | Permanent Link | Categories: IT