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

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

Please retain CCs when posting to xen-* lists, or things are liable to get
dropped.

On Fri, 2015-09-25 at 15:57 +0000, Viktor Dukhovni wrote:
> 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.ÂÂWhat can be done to avoid the grant
> table exhaustion in the first place.ÂÂAlternatively, 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.ÂÂSome 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.

I see you posted a netfront patch at some point[0], but I don't see it on
devel lists. Linux includes a file called MAINTAINERS which tells you who
(and which lists) to copy on a patch and there is a "get_maintainer.pl"
tool which can help figure it out. In this case:

    linux$ ./scripts/get_maintainer.pl -f drivers/net/xen-netfront.c 
    Konrad Rzeszutek Wilk <    konrad.wilk@xxxxxxxxxx    > (supporter:XEN 
HYPERVISOR INTERFACE)
    Boris Ostrovsky <    boris.ostrovsky@xxxxxxxxxx    > (supporter:XEN 
HYPERVISOR INTERFACE)
    David Vrabel <    david.vrabel@xxxxxxxxxx    > (supporter:XEN HYPERVISOR 
INTERFACE)
    xen-devel@xxxxxxxxxxxxxxxxxxxx     (moderated list:XEN HYPERVISOR INTERFACE)
    netdev@xxxxxxxxxxxxxxx     (open list:NETWORKING DRIVERS)
    linux-kernel@xxxxxxxxxxxxxxx     (open list)

If you think this is still an issue then please could you resubmit in the
appropriate places. You might also find Documentation/SubmittingPatches.txt
from the Linux source useful, since this is a networking patch
Documentation/networking/netdev-FAQ.txt might be of interest too.

Ian.

[0]Â
http://lists.xenproject.org/archives/html/xen-users/2015-09/txtbaRgWqxpT4.txt

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