[Xen-users] poor I/O performance with PV drivers and I/O emu

[Riccardo Veraldi <Riccardo.Veraldi@xxxxxxxxxxxx>]

Hello,
I wanted to test the disk I/O on my virtual machines using PV drivers
over HVM virtualization to see if I could get better disk IO perormances.
So I compiled and loaded the xen_vnif xend_vbd drivers ecc on my domU
and the network got a real burst in performances. The problem is disk I/O
here is my guest configuration


name = "wn-test-01"
builder = "hvm"
memory = "2048"
disk = [ 'phy:/dev/VolGroup00/test-1_disk,xvda,w' ]
vif = [ 'type=netfront, mac=00:16:3e:00:00:1f, bridge=eth0', ]
kernel = "/usr/lib/xen/boot/hvmloader"
device_model = '/usr/lib64/xen/bin/qemu-dm'
vnc=1
vncunused=1
vnclisten="0.0.0.0"
vncconsole=1
apic=1
acpi=1
pae=1
usbdevice='tablet'
boot='nc'
vcpus=1
on_reboot   = 'restart'
on_crash    = 'restart'


I am using a physical partition and exporting the disk as a xvda disc on the 
domU.
The domu can see the disk as a xvda.
So I did a test with bonnie++ and I got the same poor results as I have with 
IOEMU.
Am I missing something in the configuration or the performances are so poor also
using PV drivers for disk IO ?? is this normal ?

Sequential output around 4MB/s, Sequential input about 50MB/s

I got the same poor results using IOEMU standard emulated disks on domU.

Any hints or suggestions to leverage paravirtualized drivers performances for 
Disk I/O
on HVM virtualization ?


thanks


Rick



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