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

["Zhang, Helin" <helin.zhang@intel.com>]

For L2 RSS, I think i40e hardware supports it, which will be enabled soon later.

Regards,
Helin

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Vithal S Mohare
> Sent: Tuesday, December 23, 2014 5:38 PM
> To: Richardson, Bruce
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH RFC 0/3] DPDK ethdev callback support
> 
> 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.richardson@intel.com]
> Sent: Tuesday, December 23, 2014 3:00 PM
> To: Vithal S Mohare
> Cc: dev@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@dpdk.org] On Behalf Of Bruce Richardson
> > Sent: Monday, December 22, 2014 10:17 PM
> > To: dev@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
> >