Re: arp during live migration

[Hans-Christian Armingeon <johnny@wh-netz.de>]

Graham, Simon wrote:
>> I am having some trouble with the send_fake_arp in the netfront
>>     
> driver.
>   
>
> Interesting - I was just composing an almost identical note; we've been
> seeing some horrible network blackouts in migration that are caused by a
> failure to send the gratuitous ARP (blackouts vary from 0-50+ seconds
> when the domain is idle and just being pinged from outside).
>   

I am having the same troubles with xen 3.1 from ubuntu gutsy.
I have xen-hypervisor-3.1.0-0ubuntu18 instaled on my system.

maybe this bug has eben re-introduced? Can somebody confirm, that this 
is still working?

I am currently doing a semester thesis in measuring downtime, while 
migrating over loaded/lagged links. The goal would be trying to 
measure/estimate the migrationtime/downtime.

I see no ping reply packets, even if the domain is already up and 
running. It sakes about 10 seconsd, until I see any ping reply packets.


Hans-Christian


> In my case, I NEVER see the gratuitous ARP being sent (confirmed using
> tcpdump on peth0 in Dom0) and the return value from dev_queue_xmit is
> sometimes 0 and sometimes 2 (that's PLUS 2 -- congestion notification
> [NET_XMIT_CN]).
>
> My next step was going to be to add instrumentation to netback but I
> thought I would ask if this is a known issue with 3.0.3 first...
>
> Simon
>
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