[Xen-devel] Poor NIC performance on domUs / Crashing

[<ryan@xxxxxxxxxxxx>]

Hi All, 

Setup is as follows:

Hardware: 

AMD Sempron 2800+ (No VT) 
3GB RAM 
8x250GB IDE Drives in RAID5 

Software
Xen-3.4.1 

dom0: Gentoo built with Sources 2.6.29-r4 
domU: Gentoo built with Sources 2.6.29-r4

dom0 is running as my firewall while domU is running mail/web services.
Here's my dd tests on both the dom0 and domU:


dom0:

fs ~ # time dd if=/dev/sda of=/dev/null bs=1M count=500
500+0 records in
500+0 records out
524288000 bytes (524 MB) copied, 4.71219 s, 111 MB/s

real    0m4.718s
user    0m0.000s
sys     0m1.844s

fs ~ # time hdparm -t /dev/sda

/dev/sda:
 Timing buffered disk reads:  598 MB in  3.19 seconds = 187.22 MB/sec

real    0m6.598s
user    0m0.131s
sys     0m2.059s


domU:

mail ~ # time dd if=/dev/xvda of=/dev/null bs=1M count=500
500+0 records in
500+0 records out
524288000 bytes (524 MB) copied, 9.39719 s, 55.8 MB/s

real    0m9.404s
user    0m0.000s
sys     0m1.317s

mail ~ # time hdparm -t /dev/xvda 

/dev/xvda:
 Timing buffered disk reads:  568 MB in  3.00 seconds = 189.19 MB/sec

real    0m6.161s
user    0m0.121s
sys     0m1.789s

Here's my config file for the domU:

fs ~ # cat /etc/xen/mail
# general
name    = "mail";
memory  = 1024;

# booting
kernel  = "/mnt/data/vms/xen/kernels/vmlinuz-2.6.29-r4-xenU";

# virtual harddisk
disk = [ "file:/mnt/data/vms/mail/domU-mail,xvda,w" ];
root = "/dev/xvda ro";

# virtual network
vif = [ "ip=10.9.18.13, vifname=eth3" ];
#vif = [ "" ];
#dhcp = "dhcp";

# If you can't see anything from init in your "xm console" command try
uncommenting this line.
extra = 'xencons=tty'


When I run rsync from a network host into the domU my pings to the domU go
to 1000ms and my write speed is around 1MB/s. I've already set the ethtool
-K eth0 tx off on the domU:

mail ~ # ethtool -k eth0
Offload parameters for eth0:
Cannot get device rx csum settings: Operation not supported
rx-checksumming: off
tx-checksumming: off
scatter-gather: off
tcp segmentation offload: off
udp fragmentation offload: off
generic segmentation offload: off


Also, I've had the whole kernel crash on the dom0 when doing moderate
network activity to the domU. Got some message about insufficient memory on
the eth0 interface (WAN facing on the dom0).

Any ideas as to how to troubleshoot this?

Thanks!
Ryan

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