AIE_STREAM_STALLS - 2022.2 English

Vitis Guidance Messaging (UG1315)

Document ID
UG1315
Release Date
2022-10-19
Version
2022.2 English

Description

This rule checks the amount of stream stalls for AI Engine tiles.

Default Threshold

20.0

Explanation

Reducing stream stalls can improve AI Engine performance. Time AI Engine was in a stream stall. This could be due to multiple reasons such as streams being read faster than they are written to streams from the PL being clocked at a slower frequency, etc.

Recommendation

See this link in AI Engine Tools and Flows User Guide (UG1076) for AIE_STREAM_STALLS.

You can resolve the stall by examining stream access patterns using trace results and increasing/balancing the FIFO depth on the stream, or maximizing the PL bandwidth to the AI Engine.

  • Increase FIFO depth.
  • Adjust stream read and write instructions in the loop.
  • Multiple streams: Insert DMA FIFO or set different FIFO depth for different destination nets.
  • PLIO: maximize AIE-PL interface bandwidth. For example: 64bit interface, highest frequency(1/2 AIE frequency) for PL, BLI register (channels with it).