On 10/17/2010 08:14 AM, Miles Fidelman wrote:
Sam wrote:
On 10/16/2010 01:27 PM, Miles Fidelman wrote:
I've been getting just a little fed up with the state of Xen on Debian
Lenny - there are a couple of known bugs that lead to periodic kernel
panics - but fixes haven't made it into the Lenny distribution. I'm sort
of waiting to see how things shake out with Debian Squeeze, when it
becomes stable, but...
I have been using lenny for over a year now. I had some lockups at
first but I never could tell if it was just on vm that was crashing
and bringing the whole setup down. Since I have done cpu pinning and
better ram management, I haven't had any problems.
Based on the console errors I've seen when I have a kernel panic, and
some of the open bug reports I've seen, I'm guessing that cpu pinning
would solve my immediate problem.
But I'm not sure what an effective configuration would be - my current
environment has 2 CPUs and 5 VMs (dom0 + 4 domUs) per server. Not sure
how to set up the pinning, and I expect there would be a performance
hit. So much easier to let the hypervisor allocate CPUs dynamically - if
it worked right.
Sam... could you say a bit more about the configuration details of what
you're doing re. "cpu pinning and better ram management?"
Thanks,
Miles
I am running on a dual 1.6ghz cpu intel atom motherboard so of course
this is less than ideal. The atom cpu, even though 2 core, has hyper
threading which makes dom0 think it has 4 cpus so you have to do some
testing to figure out which cpu's are actually on a separate core. dom0
by default has access to all cores. I only have 2 domU's. One has:
cpus = "1,3"
vcpus = 2
memory = 732
while the other has:
cpus = "0,2"
vcpus = 2
memory = 732
Again, note that even though they were passed 2 cpu's, they are just
actually getting one hyperthreaded cpu core. dom0 also additionally gets
a set amount of ram at boot time.
From menu.lst:
title Xen 3.2-1-amd64 / Debian GNU/Linux, kernel
2.6.26-2-xen-amd64
root (hd0,0)
kernel /xen-3.2-1-amd64.gz dom0_mem=256M
module /vmlinuz-2.6.26-2-xen-amd64 root=/dev/mapper/vg0-xen ro
console=tty0
module /initrd.img-2.6.26-2-xen-amd64
That is not much ram for dom0, but not much is going on there in my set
up. / is only taking up 900mb. After 4 months of uptime, it finally
started using some swap (a whole 10mb). In the /etc/rc.local of dom0 I
passed "xm sched-credit -d Domain-0 -w 512" to give dom0 higher priority
over other vm's also.
So in your case I would figure out if any of your domU's are considered
"more stable" than the others. Put the domU's that you trust stability
wise on on cpu, the others on the other cpu. Of course unless they are
all equal or have the same distro, then just just put 2 on one cpu and 2
on the other. dom0 will have access to both cpus. I doubt 2 domU's on
the same core would crash at the same time and and use up all the
resources. Nothing should be crashing anyway.
I would also go with debian squeeze unless you are having trouble with
the debian installer. I normally use the net install disk
http://www.debian.org/distrib/netinst and then use aptitude to install
the rest of my packages. I don't ever use the preset tasks to install
any thing.
The wiki has some tips: http://wiki.debian.org/Xen
To install the domU's use this:
lenny:
http://ftp.debian.org/debian/dists/lenny/main/installer-i386/current/images/netboot/xen/xm-debian.cfg
sqeeze:
http://ftp.debian.org/debian/dists/squeeze/main/installer-amd64/current/images/netboot/xen/xm-debian.cfg
Of course, all of these debian ways I have showed you only involve the
console and no gui installers. If you are wanting that, you might have
to look else where.
Sam
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