[dpdk-dev] [PATCH RFC 0/3] DPDK ethdev callback support

[Bruce Richardson <bruce.richardson@intel.com>]

This RFC is for a small addition to the ethdev library, to add in support for
callbacks at the RX and TX stages. This allows packet processing to be done on
packets before they get returned to applications using rte_eth_rx_burst call.

Use case: the first use case for this is to enable a consistent set of 
packets mbufs to be received by applications irrespective of the NIC used
to receive those. For example, for a port type that does not support RSS,
a callback on RX can be configured to calculate a hash in software. 
Similarly, this mechanism can be used to add other information to mbufs
as they are received, such as timestamps or sequence numbers, without cluttering
up the main packet processing path with checks for whether packets have these
fields filled in or not.
A second use case is ease of intrumenting existing code. The example application 
shows how combining a timestamp insertion callback on RX can be paired with a 
latency calculation callback on TX to easily instrument any application for
packet latency.
A third use case is to potentially extend existing NIC capabilities beyond
what is currently supported. For example, where flow director capabilities
can match up to a certain limit of flows - in the thousands, in the case of
NICs using the ixgbe driver - a callback can extend this to potentially
millions of flows by using a software hash table lookup inline for packets
that missing the hardware lookup filters. It would all appear transparent 
to the packet handling code in the main application.

Future extensions: in future the ethdev library can be extended to provide
a standard set of callbacks for use by drivers. 

For now this patch set is RFC and still needs additional work for creating
a remove function for callbacks and to add in additional testing code.
Since this adds in new code into the critical data path, I have run some
performance tests using testpmd with the ixgbe vector drivers (i.e. the
fastest, fast-path we have :-) ). Performance drops due to this patch
seems minimal to non-existant, rough tests on my system indicate a drop
of perhaps 1%.

All feedback welcome.

Bruce Richardson (3):
  ethdev: rename callbacks field to intr_cbs
  ethdev: Add in data rxtx callback support
  examples: example showing use of callbacks.

 app/test/virtual_pmd.c                 |   2 +-
 examples/rxtx_callbacks/Makefile       |  57 +++++++++
 examples/rxtx_callbacks/basicfwd.c     | 222 +++++++++++++++++++++++++++++++++
 examples/rxtx_callbacks/basicfwd.h     |  46 +++++++
 lib/librte_ether/rte_ethdev.c          | 103 +++++++++++++--
 lib/librte_ether/rte_ethdev.h          | 125 ++++++++++++++++++-
 lib/librte_pmd_bond/rte_eth_bond_api.c |   2 +-
 7 files changed, 543 insertions(+), 14 deletions(-)
 create mode 100644 examples/rxtx_callbacks/Makefile
 create mode 100644 examples/rxtx_callbacks/basicfwd.c
 create mode 100644 examples/rxtx_callbacks/basicfwd.h

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1.9.3