bpf: Add support for fq's EDT to HBM
Adds support for fq's Earliest Departure Time to HBM (Host Bandwidth Manager). Includes a new BPF program supporting EDT, and also updates corresponding programs. It will drop packets with an EDT of more than 500us in the future unless the packet belongs to a flow with less than 2 packets in flight. This is done so each flow has at least 2 packets in flight, so they will not starve, and also to help prevent delayed ACK timeouts. It will also work with ECN enabled traffic, where the packets will be CE marked if their EDT is more than 50us in the future. The table below shows some performance numbers. The flows are back to back RPCS. One server sending to another, either 2 or 4 flows. One flow is a 10KB RPC, the rest are 1MB RPCs. When there are more than one flow of a given RPC size, the numbers represent averages. The rate limit applies to all flows (they are in the same cgroup). Tests ending with "-edt" ran with the new BPF program supporting EDT. Tests ending wit...
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