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[Xen-users] (xen) Possible bug: Memory squeeze in netback driver.

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Subject: [Xen-users] (xen) Possible bug: Memory squeeze in netback driver.
From: Erik Hensema <erik@xxxxxxxxxxx>
Date: Tue, 6 Jun 2006 20:47:44 +0200
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Hi everybody,

When I start more than about 3 domU's the following messages are 
logged in dom0:

Jun  6 18:30:03 thebe kernel: printk: 18 messages suppressed.
Jun  6 18:30:03 thebe kernel: xen_net: Memory squeeze in netback 
Jun  6 18:30:03 thebe last message repeated 9 times

This progressively gets worse when I start more and more domU's, up 
until the point some or all domU's lose their network connectivety.

When I google on the error message, a few pages turn up, but no real 

I'll try to describe my setup in detail:

the hardware:

AMD Opteron 144
4 GB ram
Dual Broadcom Corporation NetXtreme BCM5704 Gigabit Ethernet 

It's Aplus hardware from supermicro.

the software:

Suse Linux 10.1, default kernel:
Xen version 3.0.2_09656-4 (abuild@xxxxxxx) (gcc version 4.1.0 (SUSE 
Linux)) Tue May  2 01:39:27 UTC 2006

I've got two bridges: xenbr0 and xenbr1:
bridge name     bridge id               STP enabled     interfaces
xenbr0          8000.feffffffffff       no              vif0.0
(all vifX.0)
xenbr1          8000.feffffffffff       no              vif0.1
(all vifX.1)

So basically I've got two seperate lans, available to all domains. No 
NAT. One lan is an internal vlan, the other lan is the public 
Each domain runs an iptables firewall, including domain0. The firewall 
is your basic run-of-the-mill iptables firewall, rules are matching 
eth0 and eth1, no special modules are used.

domain0's got plenty of free ram when the memory squeeze happens:
thebe:~ # free -m
             total       used       free     shared    buffers  cached
Mem:          1506        646        859          0        290  101
-/+ buffers/cache:        255       1250
Swap:         4102          0       4102

Erik Hensema (erik@xxxxxxxxxxx)

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