Crate sim_pipe

Simulate a flow-controlled pipeline.

This allows the user to understand the performance impact on the pipeline of different parameters like buffer size and credit delay.

The simulation will create:

 Source -> Limiter -> FcPipeline -> Limiter -> Sink

Examples

Running a basic simulation

cargo run --bin sim-pipe --release -- --kib-to-send 1024 --stdout

Impact of buffer size

In order to see the impact of buffer size has on the throughput you can run with simulations with different buffer sizes.

If you use the default parameters you will get a pipeline which has a bandwidth of 128-bits per cycle and frames that are 128-bit (8-byte header, 8-byte payload). So the pipe will carry an entire frame every cycle.

The default pipe has a 10-entry buffer and a latency in both directions (data and credit) of 5 ticks. This results in a maximum data rate of the 14.9GiB/s.

cargo run --bin sim-pipe --release -- --kib-to-send 1024 --stdout --progress

However, if you reduce the size of the buffer in the pipeline then you will see the effective data rate reduce:

cargo run --bin sim-pipe --release -- --kib-to-send 1024 --stdout --progress --pipe-buffer-entries 9

In order to observe the bubbles in the pipeline you can use perfetto logs:

cargo run --bin sim-pipe --release -- --kib-to-send 1024 --stdout --progress --pipe-buffer-entries 9 --perfetto

Then browse to https://ui.perfetto.dev and open the trace.pftrace file that will have been generated. Within the top::pipe::credit_pipe row you will see that it drops below the maximum value.

Modules

frame_gen