Graph Execution Model - 2022.2 English

Use the following command to run AI Engine simulator:

make aiesim

Open the running result by accessing the following directory:

vitis_analyzer aiesimulator_output/default.aierun_summary

Note: The --dump-vcd option is used by aiesimulator to dump the VCD file for trace.

Click Trace view in Vitis Analyzer. Zoom in to view the first few runs of the design:

This figure lists the following events and their dependencies:

1: Tile 24_0 DMA s2mm channel 0 (s2mm.Ch0.BD0.lock0) starts. It acquires the lock of ping of input buffer (buf0) to aie_dest1 and transfers data from the PL to buf0. Refer to Graph View for the position of the buffer in the graph.

2: After DMA s2mm channel 0 completes, DMA s2mm channel 1 (s2mm.CH1.BD1.lock1) starts. It acquires the lock of pong of input buffer (buf0d) and transfers data from the PL to buf0d.

3a: The aie_dest1 kernel (in tile 25_0) acquires the lock of buf0 (shown as read lock allocated).

3b: aie_dest1 acquires the lock of ping of output buffer (buf1) as well.

4a: After aie_dest1 acquires the locks of its input buffer (buf0) and output buffer (buf1), it starts. If any lock cannot be acquired, it will run into lock stall.

4b: After tile 24_0 DMA s2mm channel 1 (s2mm.CH1.BD1.lock1) completes, it switches back to DMA s2mm channel 0 (s2mm.CH0.BD1.lock0). At first, buf0 is still read by aie_dest1 (read lock allocated), so it sticks at DMA lock req in red. After the read lock of the buffer is released, it acquires lock and starts data transfer.

5: After aie_dest1 completes, it releases the output buffer (buf1). The kernel aie_dest2 acquires the lock of buf1 (read lock allocated).

6a: After the lock of buf1 is acquired, aie_dest2 starts.

6b:. aie_dest1 acquires the lock of buf0d (read lock allocated).

6c: aie_dest1 acquires the lock of buf1d (write lock allocated).

7: After aie_dest1 acquires the locks of its input buffer (buf0d) and output buffer (buf1d), it starts.

8: After aie_dest1 completes, it releases the output buffer (buf1d). Kernel aie_dest2 acquires the lock of buf1d (read lock allocated).

9: After the lock of buf1d is acquired, aie_dest2 starts.

Note: The stream interface does not need to acquire lock; it has inherent backward and forward pressure for data synchronization. Every lock acquire and release event has some cycles of overhead.