xennetback_ifstart: no mcl_pages crashes XEN2-dom0

[Damian Lubosch <dl%xiqit.de@localhost>]

Hello!

I am using NetBSD4.0Beta as XEN2-Dom0 (from 10/4/06) with six 
NetBSD3.0.1 DomUs on an AMD 3700+ server, VIA Chipset with 1GB of RAM 
and Hardware Raid.

From time to time I get the following error that forces me to reboot my 
Dom0


May 30 10:07:42 pless /netbsd: xennetback: got only 29 new mcl pages
May 30 10:07:47 pless /netbsd: xennetback: got only 9 new mcl pages
May 30 10:07:48 pless /netbsd: xennetback: got only 3 new mcl pages
May 30 10:07:48 pless /netbsd: xennetback: got only 1 new mcl pages
May 30 10:07:48 pless /netbsd: xennetback: can't get new mcl pages (0)
May 30 10:07:48 pless /netbsd: xennetback_ifstart: no mcl_pages
And the last two lines repeat 1000+ times....

What are those mcl pages?

On the domU machines I let run a lot of RSync cronjobs copying files 
from another sibling-PC with very similar configuration. Some of the 
DomUs share directories with nfs. In fact this machine is my 
hot-standby-backup-server. The master server does not complain about 
this problem. (It only complains about ..."/netbsd: xbdback: domain 6 
sending excessively fragmented I/O" but it's not that bad I think)


First I thought that it could have to do with a buggy network driver for 
the onboard Realtec NIC but now there is an Intel NIC built in and the 
problem still persists.

My system memory is divided as follows:

pless# xm list
Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0       63    0  r----    499.4
ap-php4            3      255    0  -b---     26.0    9603
ap-php5            4      127    0  -b---     21.8    9604
dbserver           5      127    0  -b---    101.3    9605
mailserver         7      169    0  -b---     60.5    9607
ns1                2      127    0  -b---     20.4    9602
router             1      127    0  -b---    257.4    9601


pless# xm info
system                 : NetBSD
host                   : pless
release                : 4.0_BETA
version                : NetBSD 4.0_BETA (XEN2_DOM0) #0: Wed Apr 18 
15:14:53 CEST 2007  root@pless:/xen/usr/src/sys/arch/i386/compile/XEN2_DOM0
machine                : i386
cores                  : 1
hyperthreads_per_core  : 1
cpu_mhz                : 2199
memory                 : 1022
free_memory            : 2



I use an self-built kernel for this NetBSD version with more SHM pages 
(8192 instead of 2048). I hoped that could solve the problem but it did not.

options         SHMMAXPGS=8192  # 2048 pages is the default


I read on the list something about XEN-DOM0 needing 32MB for itself. 
(Date of posting: 4/15/2005 6pm from Manuel Bouyer) Does it mean that I 
have to increase my 2MB of free memory to 32? That's actually what I'd 
try next...

Another idea which will be quite time consuming and I would like to avoid:
Is it worth it to update to a newer Beta-version of NetBSD4 with a newer 
Kernel?


I really hope that there is somebody out there who can help me ;-) 
Thanks in advance!


Yours,
Damian Lubosch