[dpdk-dev] [RFC PATCH 0/6] DPDK support to bifurcated driver
nhorman at tuxdriver.com
Tue Nov 25 15:23:16 CET 2014
On Tue, Nov 25, 2014 at 10:11:16PM +0800, Cunming Liang wrote:
> This is a RFC patch set to support "bifurcated driver" in DPDK.
> What is "bifurcated driver"?
> The "bifurcated driver" stands for the kernel NIC driver that supports:
> 1. on-demand rx/tx queue pairs split-off and assignment to user space
> 2. direct NIC resource(e.g. rx/tx queue registers) access from user space
> 3. distributing packets to kernel or user space rx queues by
> NIC's flow director according to the filter rules
> Here's the kernel patch set to support.
> Usage scenario
> It's well accepted by industry to use DPDK to process fast path packets in
> user space in a high performance fashion, meanwhile processing slow path
> control packets in kernel space is still needed as those packets usually
> rely on in_kernel TCP/IP stacks and/or socket programming interface.
> KNI(Kernel NIC Interface) mechanism in DPDK is designed to meet this
> requirement, with below limitation:
> 1) Software classifies packets and distributes them to kernel via DPDK
> software rings, at the cost of significant CPU cycles and memory bandwidth.
> 2) Memory copy packets between kernel' socket buffer and mbuf brings
> significant negative performance impact to KNI performance.
> The bifurcated driver provides a alternative approach that not only offloads
> flow classification and distribution to NIC but also support packets zero_copy.
> User can use standard ethtool to add filter rules to the NIC in order to
> distribute specific flows to the queues only accessed by kernel driver and
> stack, and add other rules to distribute packets to the queues assigned to
> For those rx/tx queue pairs that directly accessed from user space,
> DPDK takes over the packets rx/tx as well as corresponding DMA operation
> for high performance packet I/O.
> What's the impact and change to DPDK
> DPDK usually binds PCIe NIC devices by leveraging kernel' user space driver
> mechanism UIO or VFIO to map entire NIC' PCIe I/O space of NIC to user space.
> The bifurcated driver PMD talks to a NIC interface using raw socket APIs and
> only mmap() limited I/O space (e.g. certain 4K pages) for accessing involved
> rx/tx queue pairs. So the impact and changes mainly comes with below:
> - netdev
> DPDK needs to create a af_packet socket and bind it to a bifurcated netdev.
> The socket fd will be used to request 'queue pairs info',
> 'split/return queue pairs' and etc. The PCIe device ID, netdev MAC address,
> numa info are also from the netdev response.
> - PCIe device scan and driver probe
> netdev provides the PCIe device ID information. Refer to the device ID,
> the correct driver should be used. And for such netdev device, the creation
> of PCIe device is no longer from scan but the on-demand assignment.
> - PCIe BAR mapping
> "bifurcated driver" maps several pages for the queue pairs.
> Others BAR register space maps to a fake page. The BAR mapping go through
> mmap on sockfd. Which is a little different from what UIO/VFIO does.
> - PMD
> The PMD will no longer really initialize and configure NIC.
> Instead, it only takes care the queue pair setup, rx_burst and tx_burst.
> The patch uses eal '--vdev' parameter to assign netdev iface name and number of
> queue pairs. Here's a example about how to configure the bifurcated driver and
> run DPDK testpmd with bifurcated PMD.
> 1. Set promisc mode
> > ifconfig eth0 promisc
> 2. Turn on fdir
> > ethtool -K eth0 ntuple on
> 3. Setup a flow director rule to distribute packets with source ip
> 0.0.0.0 to rxq No.0
> > ethtool -N eth0 flow-type udp4 src-ip 0.0.0.0 action 0
> 4. Run testpmd on netdev 'eth0' with 1 queue pair.
> > ./x86_64-native-linuxapp-gcc/app/testpmd -c 0x3 -n 4 \
> > --vdev=rte_bifurc,iface=eth0,qpairs=1 -- \
> > -i --rxfreet=32 --txfreet=32 --txrst=32
> iface and qpairs arguments above specify the netdev interface name and
> number of qpairs that user space request from the "bifurcated driver"
> 5. Setup a flow director rule to distribute packets with source ip
> 220.127.116.11 to rxq No.32. This needs to be done after testpmd starts.
> > ethtool -N eth0 flow-type udp4 src-ip 18.104.22.168 action 32
> Below illustrates the detailed changes in this patch set.
> The first two patches are all about the eal API declaration and Linux version
> definition to support af_packet socket and verbs of bifurcated netdev.
> Those APIs include the verbs like open, bind, (un)map, split/retturn, map_umem.
> And other APIs like set_pci, get_ifinfo and get/put_devargs which help to
> generate pci device from bifurcated netdev and get basic netdev info.
> The third patch is used to allow probing driver on the PCIe VDEV created from
> a NIC interface driven by "bifurcated driver". It defines a new flag
> 'RTE_PCI_DRV_BIFURC' used for direct ring access PMD.
> The library is used as a VDEV bus driver to scan '--vdev=rte_bifurc' VDEV
> from eal command-line. It generates the PCIe VDEV device ready for further
> driver probe. It maintains the bifurcated device information include sockfd,
> hwaddr, mtu, qpairs, iface_name. It's used for other direct ring access PMD
> to apply for bifurcated device info.
> direct ring access PMD
> The patch provides direct ring access PMD for ixgbe. Comparing to the normal
> PMD ixgbe, it uses 'RTE_PCI_DRV_BIFURC' flag during self registration.
> It mostly reuses the existing PMD ops to avoid re-implementing everything
> from scratch. And it also modifies the rx/tx_queue_setup to allow queue
> setup from any queue offset.
> Supported NIC driver
> The "bifurcated driver" kernel patch only supports "ixgbe" driver at the moment,
> so this RFC patch also provides "ixgbe" PMD via direct-mapped rings as sample.
> The support for 40GE(i40e) will be added in the future.
> In addition, for those multi-queues enabled NIC with flow director capability
> to do perform packet classification and distribution, there's no special
> technical gap to provide bifurcated driver approach support.
> By using "bifurcated driver", user space only takes over the DMA operation.
> For those NIC configure setting, it's out of control from user space PMD.
> All the NIC setting including add/del filter rules need to be done by
> standard Linux network tools(e.g. ethtool).
> So the feature support really depend on how much are supported by ethtool.
> Any questions, comments and feedback are welcome.
> Signed-off-by: Cunming Liang <cunming.liang at intel.com>
> Signed-off-by: Danny Zhou <danny.zhou at intel.com>
> *** BLURB HERE ***
> Cunming Liang (6):
> eal: common direct ring access API
> eal: direct ring access support by linux af_packet
> pci: allow VDEV as pci device during device driver probe
> bifurc: add driver to scan bifurcated netdev
> ixgbe: rx/tx queue stop bug fix
> ixgbe: PMD for bifurc ixgbe net device
> config/common_linuxapp | 5 +
> lib/Makefile | 1 +
> lib/librte_bifurc/Makefile | 58 +++++
> lib/librte_bifurc/rte_bifurc.c | 284 +++++++++++++++++++++
> lib/librte_bifurc/rte_bifurc.h | 90 +++++++
> lib/librte_eal/common/Makefile | 5 +
> lib/librte_eal/common/include/rte_pci.h | 4 +
> lib/librte_eal/common/include/rte_pci_bifurc.h | 186 ++++++++++++++
> lib/librte_eal/linuxapp/eal/Makefile | 1 +
> lib/librte_eal/linuxapp/eal/eal_pci.c | 42 ++--
> lib/librte_eal/linuxapp/eal/eal_pci_bifurc.c | 336 +++++++++++++++++++++++++
> lib/librte_ether/rte_ethdev.c | 3 +-
> lib/librte_pmd_ixgbe/Makefile | 13 +-
> lib/librte_pmd_ixgbe/ixgbe_bifurcate.c | 303 ++++++++++++++++++++++
> lib/librte_pmd_ixgbe/ixgbe_bifurcate.h | 57 +++++
> lib/librte_pmd_ixgbe/ixgbe_rxtx.c | 44 +++-
> lib/librte_pmd_ixgbe/ixgbe_rxtx.h | 10 +
> mk/rte.app.mk | 6 +
> 18 files changed, 1421 insertions(+), 27 deletions(-)
> create mode 100644 lib/librte_bifurc/Makefile
> create mode 100644 lib/librte_bifurc/rte_bifurc.c
> create mode 100644 lib/librte_bifurc/rte_bifurc.h
> create mode 100644 lib/librte_eal/common/include/rte_pci_bifurc.h
> create mode 100644 lib/librte_eal/linuxapp/eal/eal_pci_bifurc.c
> create mode 100644 lib/librte_pmd_ixgbe/ixgbe_bifurcate.c
> create mode 100644 lib/librte_pmd_ixgbe/ixgbe_bifurcate.h
AIUI, the bifurcated driver hasn't yet been accepted upstream, has it? Given
that, I don't think its wise to pull this in yet ahead of the kernel work, as
there may still be kernel side changes that the user space pmd will have to
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