> >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. >
I was a bit on the fence as to whether I should split this out or not myself; I'll merge this and the NEWS changes back into the feature patch. >-- >fbl _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
