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Re: [Xen-users] major slow down with xen implementation

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Subject: Re: [Xen-users] major slow down with xen implementation
From: "Nemeth, Tamas" <nice@xxxxxxxxxxxxxxx>
Date: Fri, 26 Sep 2008 10:32:43 +0200
Cc: Geoffrey <lists@xxxxxxxxxxxxxxxxxxxxx>
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Hi all,

We have similar servers, and I use xen 3.2.1 (3.3.0 seems to be too
buggy). The hypervisor is 64bit, but all domains (including dom0) are
32bit PAE, because a 64bit dom0 - for example - can't migrate a 32bit
domU, but a 32bit domU can migrate a 64bit domU, AFAIK. So, accordint to
my experiences, 32bit PAE domains (with the original xen.org kernels, if
you can afford it) running on a 64bit hypervisor seem to be the best
soulution to utilize a beast like your machine. Xen 3.2.1 seems to be
fast, and reliable.

I compiled xen the following way:
I downloaded the linux-2.6.18-xen-3.2.0 kernel and xen-3.2.1 separately,
and then first, i compiled the kernel by:

gzip -dc /proc/config.gz
make menuconfig
<SOME CONFIGURATION, especially don't forget to set "Processor type and
features" -> "High Memory Support" to 64GB in order to make it a PAE
<During the building process, i watch this video:
make install
make modules_install
mkinitrd <IN SOME WAY>

After compiling and installing the kernel, I compiled and installed xen,
but I didn't do a "make world" at all!! I did it the following way:

On a 64 bit machine, or by cross-compiling (i've personally never
tried), I build the hypervisor:
make xen #this creates only the hypervisor (/boot/xen-3.3.0.gz)
make install-xen
After installing, I copy the hypervisor (/boot/xen-3.2.1.gz) to the
32bit target dom0.

And finally I compile and install the tools on the (32bit, of course)
make tools #this creates thigs like the xm command, hvm environment,
           #network scripts, etc.

make install-tools

Best regards,


2008. 09. 25, csütörtök keltezéssel 11.22-kor Geoffrey ezt írta:
> We have some fairly robust hardware we are trying to set up a number of 
> para-virtual servers in a clustered environment and we are seeing huge 
> cpu issues.  Specs:
> Dell 1950: 8 1u servers
> cpu MHz : 2660.038
> dual quad cores
> 32G memory each
> Our first virual server was configured to use 8G and 4 cores.
> I tried running a quick test by compiling our application, simply 
> running 'time make.'  The results were terrible:
> real    0m56.79s
> user    0m26.53s
> sys     0m35.46s
> In comparison, my laptop (Intel Core2 Duo CPU @ 2.50GHz, 2G mem):
> real    0m42.99s
> user    0m29.85s
> sys     0m6.47s
> We then reconfigured the virtual server to use a single core and the 
> results were almost identical to the 4 core test.
> Any insights as to what our problem might be would be greatly appreciated.

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