As I'm currently unable to start 10 VMs with NetBSD/xen dom0 I installed
Linux (Ubuntu) on my second Dell PowerEdge and made some measurements
with Xen.

As you can see the Linux loopback filesystem (i.e. "file:/foo,wd0d,w"
in my config files) is painfully slow when multiple concurrent VMs are
running. I'm aware of LVM and other methods but I didn't want to
change any of my filesystems.

Also notice the weird user and sys times when using Linux dom0. This
must be a NetBSD bug (maybe related to port-xen/29846?).

######################################################################

Xen 2.0.5 (Linux 2.6.11 dom0)
=============================

1 x NetBSD 128 MB XENU
-----------------------------
633.85 real       539.46 user        79.03 sys

4 x NetBSD 128 MB XENU
-----------------------------
2531.43 real -1979726566.90 user 918147533.77 sys
2535.26 real 109049461.84 user 1270345770.68 sys
2535.37 real -1885868528.24 user 902858924.33 sys
2535.67 real  62835949.83 user 407690637.66 sys

10 x NetBSD 128 MB XENU
------------------------------
6381.95 real -1949221756.55 user 496956576.73 sys
6384.78 real 564466822.44 user -984601911.74 sys
6377.07 real 1828713121.00 user 1603244200.17 sys
6403.75 real -47847798.33 user -2060970139.03 sys
6396.85 real 229133955.21 user 1744388196.92 sys
6401.04 real -1261204337.20 user 990622602.92 sys
6398.02 real 1589411476.68 user -649278544.72 sys
6402.68 real 1873920550.12 user 975371233.95 sys
6401.48 real 1003653078.00 user -487867200.58 sys
6400.82 real 991093698.09 user 1406018695.37 sys

######################################################################

Xen 2.0.5 (NetBSD 3.99.3 dom0)
==============================

 > 1 x NetBSD 128 MB XENU (vnd with 2 GB file-as-disk)
 > ---------------------------------------------------
 > 492.76 real       415.54 user        61.42 sys
 >
 > 4 x NetBSD 128 MB XENU (vnd with 2 GB file-as-disk)
 > ---------------------------------------------------
 > 1633.38 real      1396.94 user       177.58 sys
 > 1641.86 real      1404.19 user       195.83 sys
 > 1642.72 real      1403.38 user       196.25 sys
 > 1633.69 real      1394.42 user       176.68 sys