On Mon, 7 Oct 2019 23:16:51 -0700, Sridhar Samudrala wrote: > This is a rework of the following patch series > https://lore.kernel.org/netdev/1565840783-8269-1-git-send-email-sridhar.samudrala@xxxxxxxxx/#r > that tried to enable direct receive by bypassing XDP program attached > to the device. > > Based on the community feedback and some suggestions from Bjorn, changed > the semantics of the implementation to enable direct receive on AF_XDP > sockets that are bound to a queue only when there is no normal XDP program > attached to the device. > > This is accomplished by introducing a special BPF prog pointer (DIRECT_XSK) > that is attached at the time of binding an AF_XDP socket to a queue of a > device. This is done only if there is no other XDP program attached to > the device. The normal XDP program has precedence and will replace the > DIRECT_XSK prog if it is attached later. The main reason to introduce a > special BPF prog pointer is to minimize the driver changes. The only change > is to use the bpf_get_prog_id() helper when QUERYING the prog id. > > Any attach of a normal XDP program will take precedence and the direct xsk > program will be removed. The direct XSK program will be attached > automatically when the normal XDP program is removed when there are any > AF_XDP direct sockets associated with that device. > > A static key is used to control this feature in order to avoid any overhead > for normal XDP datapath when there are no AF_XDP sockets in direct-xsk mode. Don't say that static branches have no overhead. That's dishonest. > Here is some performance data i collected on my Intel Ivybridge based > development system (Intel(R) Xeon(R) CPU E5-2697 v2 @ 2.70GHz) > NIC: Intel 40Gb ethernet (i40e) > > xdpsock rxdrop 1 core (both app and queue's irq pinned to the same core) > default : taskset -c 1 ./xdpsock -i enp66s0f0 -r -q 1 > direct-xsk :taskset -c 1 ./xdpsock -i enp66s0f0 -r -q 1 > 6.1x improvement in drop rate > > xdpsock rxdrop 2 core (app and queue's irq pinned to different cores) > default : taskset -c 3 ./xdpsock -i enp66s0f0 -r -q 1 > direct-xsk :taskset -c 3 ./xdpsock -i enp66s0f0 -r -d -q 1 > 6x improvement in drop rate > > xdpsock l2fwd 1 core (both app and queue's irq pinned to the same core) > default : taskset -c 1 ./xdpsock -i enp66s0f0 -l -q 1 > direct-xsk :taskset -c 1 ./xdpsock -i enp66s0f0 -l -d -q 1 > 3.5x improvement in l2fwd rate > > xdpsock rxdrop 2 core (app and queue'sirq pinned to different cores) > default : taskset -c 3 ./xdpsock -i enp66s0f0 -l -q 1 > direct-xsk :taskset -c 3 ./xdpsock -i enp66s0f0 -l -d -q 1 > 4.5x improvement in l2fwd rate I asked you to add numbers for handling those use cases in the kernel directly. > dpdk-pktgen is used to send 64byte UDP packets from a link partner and > ethtool ntuple flow rule is used to redirect packets to queue 1 on the > system under test. Obviously still nack from me.
