On Tue, 16 Feb 2016 11:31:50 +0000 Mark Kavanagh <mark.b.kavan...@intel.com> wrote:
> Signed-off-by: Mark Kavanagh <mark.b.kavan...@intel.com> > --- > INSTALL.DPDK.md | 59 > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 59 insertions(+) > > diff --git a/INSTALL.DPDK.md b/INSTALL.DPDK.md > index 722fb9e..4ca98cb 100644 > --- a/INSTALL.DPDK.md > +++ b/INSTALL.DPDK.md > @@ -878,6 +878,60 @@ by adding the following string: > to <interface> sections of all network devices used by DPDK. Parameter 'N' > determines how many queues can be used by the guest. > > +Jumbo Frames > +------------ > + > +Support for Jumbo Frames may be enabled at run-time for DPDK-type ports. > + > +To avail of Jumbo Frame support, add the 'mtu_request' option to the > ovs-vsctl > +'add-port' command-line, along with the required MTU for the port. > +e.g. > + > + ``` > + ovs-vsctl add-port br0 dpdk0 -- set Interface dpdk0 type=dpdk > options:mtu_request=9000 > + ``` > + > +When Jumbo Frames are enabled, the size of a DPDK port's mbuf segments are > +increased, such that a full Jumbo Frame may be accommodated inside a single > +mbuf segment. Once set, the MTU for a DPDK port is immutable. > + > +Note that from an OVSDB perspective, the `mtu_request` option for a specific > +port may be disregarded once initially set, as subsequent modifications to > this > +field are disregarded by the DPDK port. As with non-DPDK ports, the MTU of > DPDK > +ports is reported by the `Interface` table's `mtu` field. > + > +Jumbo frame support has been validated against 13312B frames, using the > +DPDK `igb_uio` driver, but larger frames and other DPDK NIC drivers may > +theoretically be supported. Supported port types excludes vHost-Cuse ports, > as > +that feature is pending deprecation. > + > +vHost Ports and Jumbo Frames > +---------------------------- > +Jumbo frame support is available for DPDK vHost-User ports only. Some > additional > +configuration is needed to take advantage of this feature: > + > + 1. `mergeable buffers` must be enabled for vHost ports, as demonstrated in > + the QEMU command line snippet below: > + > + ``` > + '-netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce \' > + '-device > virtio-net-pci,mac=00:00:00:00:00:01,netdev=mynet1,mrg_rxbuf=on' > + ``` > + > + 2. Where virtio devices are bound to the Linux kernel driver in a guest > + environment (i.e. interfaces are not bound to an in-guest DPDK driver), > the > + MTU of those logical network interfaces must also be increased. This > + avoids segmentation of Jumbo Frames in the guest. Note that 'MTU' refers > + to the length of the IP packet only, and not that of the entire frame. > + > + e.g. To calculate the exact MTU of a standard IPv4 frame, subtract the > L2 > + header and CRC lengths (i.e. 18B) from the max supported frame size. > + So, to set the MTU for a 13312B Jumbo Frame: > + > + ``` > + ifconfig eth1 mtu 13294 > + ``` > + > Restrictions: > ------------- > > @@ -921,6 +975,11 @@ Restrictions: > the next release of DPDK (which includes the above patch) is available > and > integrated into OVS. > > + Jumbo Frames: > + - `virtio-pmd`: DPDK apps in the guest do not exit gracefully. This is a > DPDK > + issue that is currently being investigated. > + - vHost-Cuse: Jumbo Frame support is not available for vHost Cuse ports. > + > Bug Reporting: > -------------- > This should be in the patch adding the feature. The rationale is that if you bisect you can't have the code without the documentation. -- fbl _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
