On Mon, Dec 22, 2014 at 10:31:57AM -0800, Stephen Hemminger wrote: > On Mon, 22 Dec 2014 16:47:21 +0000 > Bruce Richardson <bruce.richardson at intel.com> wrote: > > > 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 > > > > What about SMP safety? The callback list is not thread safe. > Do you plan to start integrating with an RCU framework like userspace RCU?
I hadn't considered multiple CPUs adding removing callbacks simultaneously. I'll look into it. /Bruce
