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Re: [Xen-devel] Re: [ANNOUNCE] virtbench now has xen support

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] Re: [ANNOUNCE] virtbench now has xen support
From: Jan Michael <jan.michael@xxxxxxx>
Date: Wed, 23 May 2007 20:05:27 +0200
Cc: Anthony Liguori <aliguori@xxxxxxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, Xen Mailing List <xen-devel@xxxxxxxxxxxxxxxxxxx>
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as I found out it is a little bit tricky to use one's initrd. Because Virtbench is overriding the init command in the domU configuration file with rdinit and therefore it is not possible to load modules:

extra = "rdinit=/virtclient @VIRTBENCH_ID@ @SERVERIP@ @SERVERPORT@ /dev/xvda1 202 1 eth0 %s" % string.replace('@IP@', '.', '/')

The template file virtbench-xen.cfg.in is used to create an individual xen configuration file for each user domain. Despite this I tried to get the virtclient working with my own initrd. I was able to successfully load the xen network and block device driver. At the end of the init script I could start virtclient from the ramdisk.

So I modified the start_machine script in that way that it will manipulate the init start script of the ramdisk and after that it creates one initrd for each domU. The domU configuration uses now a prepared ramdisk rather than this one from virtbench.

The benchmark passed with the following outcome:

Time for one context switch via pipe: 8734 (8640 - 9575)
Time for one Copy-on-Write fault: 5898 (5814 - 8963)
Time to exec client once: 573046 (565921 - 615390)
Time for one fork/exit/wait: 347687 (345750 - 362250)
Time to send 4 MB from host: 55785000 (27069625 - 315191500)
Time for one int-0x80 syscall: 370 (370 - 403)
Time for one syscall via libc: 376 (376 - 377)
Time to walk linear 64 MB: 1790875 (1711750 - 3332875)
Time to walk random 64 MB: 2254500 (2246000 - 2266250)
Time for one outb PIO operation: 721 (717 - 733)
DISABLED pte-update: glibc version is too old
Time to read from disk (256 kB): 18810406 (14266718 - 24088906)
Time for one disk read: 56343 (38593 - 201718)
DISABLED vmcall: not a VT guest
DISABLED vmmcall: not an SVM guest
Time to send 4 MB between guests: 94326750 (79872250 - 729306500)
Time for inter-guest pingpong: 130316 (119722 - 186511)
Time to sendfile 4 MB between guests: 134768000 (86528000 - 417646000)
Time to receive 1000 1k UDPs between guests: 26010000 (23384000 - 66784000)

Last question for today: What is the unit of these time values?



On 22.05.2007, at 11:33, Jeremy Fitzhardinge wrote:
Jan Michael wrote:
I can say that we are using a kernel builf from the attached kernel
config and a special initrd image for our domUs.
The initrd image contains the modules xenblk.ko and xennet.ko. So
netfront and blkfront are not compiled into the kernel.

Modular is OK if they're in the initrd you're using.

Our linux gurus made the kernel and the initrd image. I think I have
to integrate those modules into the initrd image you are using and
have to load them. But at this point I have no knowledge how to do

It's distro-dependent, but mkinitrd works for RH-type systems.
Something like "mkinitrd --with=xenblk --with=xennet -v my-initrd.img
<kernel version>".


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