Loop-aware instruction scheduling with dynamic contention tracking for tiled dataflow architectures

Abstract

Increasing on-chip wire delay along with the distributed nature of processing elements, makes instruction scheduling for tiled dataflow architectures very crucial. Our analysis reveals that careful placement of frequently executed sections of applications, and dynamic resource contention tracking can significantly improve the performance of the application. The former reduces the operand network latency, while the latter reduces stalls due to contention for processing elements. We augment one of the most recent instruction scheduling algorithms - hierarchical instruction scheduling - to better exploit spatial locality between instructions within a loop, thereby reducing expensive communication overhead by 6.5% and increasing average IPC by 5.13%. Secondly, in the presence of conditional branches and variable latency memory instructions, estimating resource contention, at compile time, is not only complex but also imperfect. We suggest dynamic tracking of contending instructions, and their re-location, once a contention threshold is exceeded. Results showed that dynamic contention tracking reduced the average ALU conflicts by 23%, thereby improving the average IPC by 14.22%. Combined together, these augmentations improve the average IPC by 19.39% and over 30% for some benchmarks. © 2009 Springer Berlin Heidelberg.