Re: [Xen-users] [Xen-devel] [BUG] 16 vcpus + 2 vif bridge = issue ?

[Viktor Dukhovni <ietf-dane@xxxxxxxxxxxx>]

On Fri, Sep 25, 2015 at 11:45:06AM +0100, Wei Liu wrote:

> > +xen_netfront: can't alloc rx grant refs
> > +net eth1: only created 15 queues
> 
> This is multiqueue exhausting grant table references.
> 
> You're supposed to be able to set a netback parameter to control default
> number of maximum queues get created. Unfortunately there is a bug in
> the code which renders the setting of that parameter when loading
> netback useless.
> 
> A workaround is to
> 
> 1. Insert netback in Dom0.
> 2. echo $NR_MAX_QUEUES_YOU_WANT > 
> /sys/module/xen_netback/parameters/max_queues
> 3. Start guest.

Surely this is not a solution.  What can be done to avoid the grant
table exhaustion in the first place.  Alternatively, the code should
avoid requesting too many queues.

I've posted a patch that may help to deal with partial allocation,
but don't know whether it is reasonable.  Some feedback on that
would sure be nice.

> Patches to both netback and netfront were merged some time ago. I'm not
> sure when they will trickle down to your distro.

Those patches don't seem to address incorrect behaviour when the
grant tables are exhausted.

-- 
        Viktor.

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