[tlug] Xen and SMP

[Curt Sampson <cjs@example.com>]

I've been once again poking a bit at xen, and I'm curious as to its SMP
behaviour. I booted up the Xen 2.5 live CD on a dual-core AMD system,
and it appeared to me, according to the monitor display, to assign
domains to either one or the other CPU, and then just stick them there.
In my case, domains 0 and 3 were on CPU 0, and 1, 2 and 4 were on CPU 1.
I then started up "while true; do true; done" on 1, 2 and 4 that started
eating up lots of CPU on those machines, but all three domains stayed
on CPU 1, getting about 1.6s each out of every 5s, and doms 0 and 2 sat
there barely ticking, as expected. Starting the same loop on dom 3 found
it getting about 5/5s, a rather unfair share!

This was Xen2; does it not move a domain from one CPU to another after
it's been started? I gather Xen3 does this (as well as providing
multiple CPUs to domains); does that compensate for it otherwise (so I
hear) being somewhat slower?

cjs
-- 
Curt Sampson       <cjs@example.com>        +81 90 7737 2974   
Mobile sites and software consulting: http://www.starling-software.com