From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wei Liu <wei.liu2@citrix.com>
Subject: Re: netfront/netback multiqueue exhausting grants
Date: Thu, 21 Jan 2016 10:52:15 +0000
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To: Ian Campbell <ian.campbell@citrix.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>, Wei Liu <wei.liu2@citrix.com>, David Vrabel <david.vrabel@citrix.com>, xen-devel <xen-devel@lists.xen.org>
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On Thu, Jan 21, 2016 at 10:37:51AM +0000, Ian Campbell wrote:
> On Thu, 2016-01-21 at 10:25 +0000, Wei Liu wrote:
> > On Thu, Jan 21, 2016 at 10:12:27AM +0000, Ian Campbell wrote:
> > [...]
> > > > I've asked the reporter to send logs for the 4.4 case to xen-devel.
> > > 
> > > User confirmed[0] that 4.4 is actually OK.
> > > 
> > > Did someone request stable backports yet, or shall I do so?
> > > 
> > 
> > I vaguely remember we requested backport for relevant patches long time
> > ago, but I admit I have lost track. So it wouldn't hurt if you do it
> > again.
> 
> So I think we'd be looking for:
> 
> 32a8440 xen-netfront: respect user provided max_queues
> 4c82ac3 xen-netback: respect user provided max_queues
> ca88ea1 xen-netfront: update num_queues to real created
> 
> which certainly resolves things such that the workarounds work, and I think
> will also fix the default case such that it works with up to 32 vcpus
> (although it will consume all the grants and only get 31/32 queues).
> 
> Does that sound correct?
> 

Yes, it does.

> As Annie said, we may still want to consider what a sensible default max
> queues would be.
> 

Maybe we should set a cap to 8 or 16 by default.

Wei.

> Ian.