Overview ======== This patchset introduces support for multi-segment mbufs to OvS-DPDK. Multi-segment mbufs are typically used when the size of an mbuf is insufficient to contain the entirety of a packet's data. Instead, the data is split across numerous mbufs, each carrying a portion, or 'segment', of the packet data. mbufs are chained via their 'next' attribute (an mbuf pointer).
Use Cases ========= i. Handling oversized (guest-originated) frames, which are marked for hardware accelration/offload (TSO, for example). Packets which originate from a non-DPDK source may be marked for offload; as such, they may be larger than the permitted ingress interface's MTU, and may be stored in an oversized dp-packet. In order to transmit such packets over a DPDK port, their contents must be copied to a DPDK mbuf (via dpdk_do_tx_copy). However, in its current implementation, that function only copies data into a single mbuf; if the space available in the mbuf is exhausted, but not all packet data has been copied, then it is lost. Similarly, when cloning a DPDK mbuf, it must be considered whether that mbuf contains multiple segments. Both issues are resolved within this patchset. ii. Handling jumbo frames. While OvS already supports jumbo frames, it does so by increasing mbuf size, such that the entirety of a jumbo frame may be handled in a single mbuf. This is certainly the preferred, and most performant approach (and remains the default). However, it places high demands on system memory; multi-segment mbufs may be prefereable for systems which are memory-constrained. Enabling multi-segment mbufs ============================ Multi-segment and single-segment mbufs are mutually exclusive, and the user must decide on which approach to adopt on init. The introduction of a new OVSDB field, 'dpdk-multi-seg-mbufs', facilitates this. This is a global boolean value, which determines how jumbo frames are represented across all DPDK ports. In the absence of a user-supplied value, 'dpdk-multi-seg-mbufs' defaults to false, i.e. multi-segment mbufs must be explicitly enabled / single-segment mbufs remain the default. Setting the field is identical to setting existing DPDK-specific OVSDB fields: ovs-vsctl set Open_vSwitch . other_config:dpdk-init=true ovs-vsctl set Open_vSwitch . other_config:dpdk-lcore-mask=0x10 ovs-vsctl set Open_vSwitch . other_config:dpdk-socket-mem=4096,0 ==> ovs-vsctl set Open_vSwitch . other_config:dpdk-multi-seg-mbufs=true --- v5: - Rebased on master e5e22dc ("datapath-windows: Prevent ct-counters from getting redundantly incremented"); - Sugesh's comments have been addressed: - Changed dp_packet_set_data() and dp_packet_set_size() logic to make them independent of each other; - Dropped patch 3 now that dp_packet_set_data() and dp_packet_set_ size() are independent; - dp_packet_clone_with_headroom() now has split functions for handling DPDK sourced packets and non-DPDK packets; - Modified various functions in dp-packet.h to account for multi-seg mbufs - dp_packet_put_uninit(), dp_packet_tail(), dp_packet_tail() and dp_packet_at(); - Added support for shifting packet data in multi-seg mbufs, using dp_packet_shift(); - Fixed some minor inconsistencies. Note that some of the changes in v5 have been contributed by Mark Kavanaugh as well. v4: - restructure patchset - account for 128B ARM cacheline when sizing mbufs Mark Kavanagh (5): netdev-dpdk: fix mbuf sizing dp-packet: init specific mbuf fields to 0 dp-packet: Add support for multi-seg mbufs netdev-dpdk: copy large packet to multi-seg. mbufs netdev-dpdk: support multi-segment jumbo frames Michael Qiu (2): dp-packet: copy mbuf info for packet copy dp-packet: copy data from multi-seg. DPDK mbuf Tiago Lam (1): dp-packet: Fix data_len issue with multi-seg mbufs NEWS | 1 + lib/dp-packet.c | 118 ++++++++++++++++++++++++++++---- lib/dp-packet.h | 189 ++++++++++++++++++++++++++++++++++++--------------- lib/dpdk.c | 7 ++ lib/netdev-dpdk.c | 183 +++++++++++++++++++++++++++++++++++++++---------- lib/netdev-dpdk.h | 1 + vswitchd/vswitch.xml | 20 ++++++ 7 files changed, 415 insertions(+), 104 deletions(-) -- 2.7.4 _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev