On Tue, Aug 13, 2019 at 09:05:44PM +0900, Toshiaki Makita wrote: > This is a rough PoC for an idea to offload TC flower to XDP. ... > xdp_flow TC ovs kmod > -------- -------- -------- > 4.0 Mpps 1.1 Mpps 1.1 Mpps Is xdp_flow limited to 4 Mpps due to veth or something else? > > So xdp_flow drop rate is roughly 4x faster than software TC or ovs kmod. > > OTOH the time to add a flow increases with xdp_flow. > > ping latency of first packet when veth1 does XDP_PASS instead of DROP: > > xdp_flow TC ovs kmod > -------- -------- -------- > 25ms 12ms 0.6ms > > xdp_flow does a lot of work to emulate TC behavior including UMH > transaction and multiple bpf map update from UMH which I think increases > the latency. make sense, but why vanilla TC is so slow ? > * Implementation > > xdp_flow makes use of UMH to load an eBPF program for XDP, similar to > bpfilter. The difference is that xdp_flow does not generate the eBPF > program dynamically but a prebuilt program is embedded in UMH. This is > mainly because flow insertion is considerably frequent. If we generate > and load an eBPF program on each insertion of a flow, the latency of the > first packet of ping in above test will incease, which I want to avoid. I think UMH approach is a good fit for this. Clearly the same algorithm can be done as kernel code or kernel module, but bpfilter-like UMH is a safer approach. > - patch 9 > Add tc-offload-xdp netdev feature and hooks to call xdp_flow kmod in > TC flower offload code. The hook into UMH from TC looks simple. Do you expect the same interface to be reused from OVS ? > * About alternative userland (ovs-vswitchd etc.) implementation > > Maybe a similar logic can be implemented in ovs-vswitchd offload > mechanism, instead of adding code to kernel. I just thought offloading > TC is more generic and allows wider usage with direct TC command. > > For example, considering that OVS inserts a flow to kernel only when > flow miss happens in kernel, we can in advance add offloaded flows via > tc filter to avoid flow insertion latency for certain sensitive flows. > TC flower usage without using OVS is also possible. > > Also as written above nftables can be offloaded to XDP with this > mechanism as well. Makes sense to me. > bpf, hashtab: Compare keys in long 3Mpps vs 4Mpps just from this patch ? or combined with i40 prefech patch ? > drivers/net/ethernet/intel/i40e/i40e_txrx.c | 1 + Could you share "perf report" for just hash tab optimization and for i40 ? I haven't seen memcmp to be bottle neck in hash tab. What is the the of the key?
