From mboxrd@z Thu Jan 1 00:00:00 1970 From: Leon Romanovsky Subject: Re: [PATCH rdma-next V1 1/9] IB/ipoib: Add warning message when changing the MTU in UD over the max range Date: Fri, 13 Jan 2017 22:31:27 +0200 Message-ID: <20170113203127.GT20392@mtr-leonro.local> References: <20161228124728.26619-1-leon@kernel.org> <20161228124728.26619-2-leon@kernel.org> <1484246776.123135.19.camel@redhat.com> <20170112193508.GO20392@mtr-leonro.local> <20170112201622.GA14584@obsidianresearch.com> <20170113150824.GQ20392@mtr-leonro.local> <20170113171234.GA30551@obsidianresearch.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="+d/sD+4Memv8CeGA" Return-path: Content-Disposition: inline In-Reply-To: <20170113171234.GA30551-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Gunthorpe Cc: Doug Ledford , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Feras Daoud , Noa Osherovich List-Id: linux-rdma@vger.kernel.org --+d/sD+4Memv8CeGA Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Fri, Jan 13, 2017 at 10:12:34AM -0700, Jason Gunthorpe wrote: > On Fri, Jan 13, 2017 at 05:08:24PM +0200, Leon Romanovsky wrote: > > On Thu, Jan 12, 2017 at 01:16:22PM -0700, Jason Gunthorpe wrote: > > > On Thu, Jan 12, 2017 at 09:35:08PM +0200, Leon Romanovsky wrote: > > > > > > > > > In datagram mode, the IB UD (Unreliable Datagram) transport is used > > > > > > so the MTU of the interface is equal to the IB L2 MTU minus the > > > > > > IPoIB encapsulation header. Any request to change the MTU value > > > > > > above the maximum range will change the MTU to the max allowed, but > > > > > > will not show any warning message. An ipoib_warn is issued in such > > > > > > cases, letting the user know that even though the value is legal, > > > > > > it can't be currently applied. > > > > > > How does RC mode work then? > > > > RC mode doesn't have limitation on MTU size and it allows messages > > larger than IB link-layer MTU. > > This is about what happens if the multicast MTU < unicast MTU - which > is *exactly* the same case on RC and UD. > > IPoIB cannot send a 64k multicast MTU on RC either. Multicast is sent in datagram despite being in connected mode and for datagram the MTU is limited by IB --+d/sD+4Memv8CeGA Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEkhr/r4Op1/04yqaB5GN7iDZyWKcFAlh5OR8ACgkQ5GN7iDZy WKdB5A/9HKM+0OJG499WUSqKZswe0aDTd3cGe1xXTQd+WNJwMfiaNjDY3RxOnps4 J4I/p9pjtt6SsVQY5j9+VCO9eDFgTUskoMe4nxanh39NqGBM8oEKWYZcIjjPyv+N tkiE8V58kxoodS36OZW+ToIsdGYzhXhgx1TXr7h/uZLfV8VoSfCx2mxkxwUz3JIL dgLoBVDHvCjs5Wj0xF0ii+InfVZDNZGxSw0ENCtythyTt6ReoAzqmlQF/36uNA/Z /FxhMXickVQAnvjLq0w7ZgPKxohRgzJDPnrgeHsCMGHND+oATOR7LcIuTWVF1Wbx qXEflc/FZiHGOVf//vwvelLqGLIXFIfxLROl5yUz/+hZSDpSWgoXn/ur2/7t2S9c H5l/Od4w3Jn7SbLlW3h/4HvgJ6R7cS2aJp/qZMLEXttstBwcvO/JYQBaUz1rBpzB nU4BhoJ3dGerzN4SkbbR5b+YdbXC5QFSZAevzFRUN0uVVklZYrS20+1in4uMpxG1 boPzvJnGFBU+lf38DGhTcT9+od/hHAD6EQKgERzT5cTLxAylzqQOGOR01Bdnupm9 nhucKtLfeW92rj/Te2TBYqzz3GmaU9vgK/MPu+RQm6rCLep8Sh+UwUujVaBrwH4W Nr8HFyD7Ctovoxii5ikbrMSN/XYom7YdhD84GLelTbyNpwd3KPY= =i6fy -----END PGP SIGNATURE----- --+d/sD+4Memv8CeGA-- -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html