Agree. As the mbuf is already received in the rx-q, may not yield great advantage. On side note, any plans to support RSS for L2 packets ?
-----Original Message----- From: Bruce Richardson [mailto:bruce.richard...@intel.com] Sent: Tuesday, December 23, 2014 3:00 PM To: Vithal S Mohare Cc: dev at dpdk.org Subject: Re: [dpdk-dev] [PATCH RFC 0/3] DPDK ethdev callback support On Tue, Dec 23, 2014 at 04:23:21AM +0000, Vithal S Mohare wrote: > Hi Bruce, > > <snip> > For example, for a port type that does not support RSS, a callback on RX can > be configured to calculate a hash in software. > </snip> > > Wondering if this callback will also be useful to bridge the gap of no RSS > support for L2 packets. i.e. in the rx call-back handler, can applications > calculate hash and feed it back so that spraying happens based on this? Now, > all pure L2 packets (e.g. arp pkts) comes to rx-q 0 of the 'port'. Adding > callback to [port][rx-q:0] would help? > > Thanks, > -Vithal Yes, that could work. The downside is that it is no faster than having an app do the calculation itself, it's just perhaps a little easier to work with in the app. /Bruce > > -----Original Message----- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Bruce Richardson > Sent: Monday, December 22, 2014 10:17 PM > To: dev at dpdk.org > Subject: [dpdk-dev] [PATCH RFC 0/3] DPDK ethdev callback support > > 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 > > -- > 1.9.3 >
