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Re: [Xen-users] Strange Network behaviour

To: hbh@xxxxxx
Subject: Re: [Xen-users] Strange Network behaviour
From: Pasi Kärkkäinen <pasik@xxxxxx>
Date: Tue, 15 Sep 2009 13:17:18 +0300
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On Tue, Sep 15, 2009 at 12:09:10PM +0200, hbh@xxxxxx wrote:
> Hi,
> thanks for the hints.
> > What does "xm info" say about free memory before and after starting the
> > 14th domU?
> It is the same line:
> Domain-0        0      478     8 r----- 357306.0
> > Does your dom0 memory get ballooned (too much) down? Check the amount of
> > dom0 memory aswell before and after 14th domU.
> > Anything in dom0 logs? dmesg? /var/log/messages file? 
> A dmesg is interesting:
> ...
> ADDRCONF(NETDEV_CHANGE): vif55.0: link becomes ready
> xenbr0: port 14(vif55.0) entering learning state
> xenbr0: topology change detected, propagating
> xenbr0: port 14(vif55.0) entering forwarding state
> printk: 126 messages suppressed.
> xen_net: Memory squeeze in netback driver.
> printk: 4 messages suppressed.
> xen_net: Memory squeeze in netback driver.
> printk: 4 messages suppressed.
> ...
> xenbr0: port 14(vif55.0) entering disabled state
> xenbr0: port 14(vif55.0) entering disabled state
> device vif55.0 left promiscuous mode
> This is from start to end of 14th domU. So i guess there is a problem with 
> the network configuration.
> In xend-config I have "(dom0-min-mem 0)"
> Shoud I set dom0 memory via boot-parameter? I found that solution on the net. 
> Which value whould be best then?

I always set dom0_mem boot parameter for Xen hypervisor, so dom0 gets
allocated dedicated amount of memory. And I make sure the other guests
only use the free/available memory, so there's no need to balloon down
dom0 memory.

Sometimes you might get problems if during the dom0 boot you have full
amount of memory visible to dom0, and the dom0 kernel network etc
parameters are calculated based on that memory amount - and then later 
dom0 memory gets ballooned way down from the original amount when you 
create the guests - but the dom0 kernel parameters are still for the original 
big amount of memory..

Dunno if that's the problem here, but could be.

-- Pasi

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