Re: [PATCH] IB/ipoib: Change To max_cm_mtu when changing mode to connected

[Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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On Mon, 2015-06-08 at 15:07 -0600, Jason Gunthorpe wrote:
> On Mon, Jun 08, 2015 at 05:04:42PM -0400, Doug Ledford wrote:
> > On Mon, 2015-06-08 at 10:42 -0600, Jason Gunthorpe wrote:
> > > On Sun, Jun 07, 2015 at 01:36:11PM +0300, Erez Shitrit wrote:
> > > > 
> > > > When switching between modes (datagram / connected) change the MTU
> > > > accordingly.
> > > > datagram mode up to 4K, connected mode up to (64K - 0x10).
> > > 
> > > Is this a bug fix (describe the user visible impact)? Should it go to
> > > -stable? Add a Fixes: line?
> > 
> > I'm not sure I would call it a bug.  Setting the MTU to max
> > automatically is a policy decision more than anything else.  Currently,
> > you have to enable connected mode, then set the MTU.  Both initscripts
> > and NetworkManager do this for you on Red Hat, so the user sees no
> > difference here.  I can't speak to other OSes.  I'm OK with setting
> > connected mode MTU to max by default once we get the scatter/gather
> > support for IPoIB added.
> 
> I was thinking about the other direction, what happens when you turn
> connected mode off?

It drops back down to IB MTU - 4.

-- 
Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
              GPG KeyID: 0E572FDD


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