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[Xen-users] GPLPV drivers problem

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] GPLPV drivers problem
From: Luís Fernandes <lfernandes@xxxxxxxx>
Date: Mon, 5 Jan 2009 18:15:29 +0000
Delivery-date: Mon, 05 Jan 2009 10:16:22 -0800
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Hello.
I've been using Xen with some virtual machines for at least 2 years now. When we all gone to VT-X, the xen world was introduced to windows and we all enjoyed that... until we realized we needed drivers for it to work =) We need to thank to James Harper for his efforts in making the GPL PV drivers, so thanks!

Since the beginning of the GPLPV drivers development i've been gathering feedback from all the users in the mailing list and some months ago i've finally installed PV drivers 0.9.11-pre18. But the performance was the same as without them, slow and with kernel times almost at 100%. I've tried solving it but never got anywhere, but the drivers remained installed.

Today I installed 0.9.12-pre13 to test the performance - again the performance is very similar with or without the pv drivers (screenshot of device manager: http://uplink.lvengine.com/device.jpg ) I've benchmarked the network with iperf between Xen virtual machines (pv machines, not hvm) and I get 2.5gbps ~ 3.0gbps, but with windows I get around 40mb/s. My kernel times are almost 100% all the time and disk performance is relatively slow (benchmarked with some windows app, hd_speed, got me around 11mb/s - not bad, but the kernel times are always up there... see http://uplink.lvengine.com/disk.jpg for a screenshot).

I use Xen 3.2.1, on a gentoo linux, so xen is compiled from source (for gentoo people, I have ioemu and pygrub use flags). I'm using kernel 2.6.21 - I think this patchset was made by Red Hat, and recently gentoo masked this version (or the version was already masked), but i needed to use the .21 kernel because .18 doesn't have support for one of my nic's and for the sata driver I think.

My windows-server config is based on the default python script :
#  -*- mode: python; -*-
import os, re
arch = os.uname()[4]
if re.search('64', arch):
    arch_libdir = 'lib64'
else:
    arch_libdir = 'lib'
kernel = "/usr/lib/xen/boot/hvmloader"
builder='hvm'
memory = 1532
shadow_memory = 16
name = "windows"
vcpus=1
pae=0
acpi=1
apic=1
vif = [ 'bridge=eth0, mac=00:16:3e:00:00:10' ]
disk = [ 'phy:/dev/windows-server/winz,hda,w','phy:/dev/atf-vg/ phc,hdb,w' ]
on_poweroff = 'destroy'
on_reboot   = 'restart'
on_crash    = 'restart'
device_model = '/usr/' + arch_libdir + '/xen/bin/qemu-dm'
boot="dc"
sdl=0
vnc=1
vnclisten="0.0.0.0"
localtime=1
usb=1
usbdevice='host:04b9:0300'
keymap='pt'

I use LVM in all partitions.

I've tried using ioemu: in the "hda" device and it's the same. I've removed the /gplpv entry from boot.ini as -pre13 doesn't need it anymore. I must be configuring something wrong, maybe it's the ACPI Multiprocessor PC kernel? (I installed this system a long time ago, before the PV drivers - changing the acpi setting now could be bad... - but if it must, I can try changing it...) Something odd is that cpu-z reports to me that the cpu has only 812mhz, but windows detects it's a 2.24ghz processor (single processor, i know the drivers have problems with smp and I don't need smp anyway)

I basically only run SQL server in this machine, and for a machine with 1.5gb of memory it runs really slow :/

Can anyone help me ?

Thanks in advance,
Luís
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