derek.holloway
7502bf64a4
L2/L1 Bottleneck Workloads
HIP workloads targeting MI350 L2 backpressure and L1 stall metrics (≥10%).
Workload Target
+--------------------------+--------------------------------------------------------------------------------------------------+-------------------------------------------+ | Workload | Baseline (intended effect) | Optimized (intended effect) | +--------------------------+--------------------------------------------------------------------------------------------------+-------------------------------------------+ | gl2_backpressure | Uncoalesced + large stride -> L2 misses -> fill LFIFO -> TCP stalls. | Shared mem, minimal L2 traffic. | +--------------------------+--------------------------------------------------------------------------------------------------+-------------------------------------------+ | L1_stall_microbenchmark | Many scattered loads/stores -> VMEM issues many commands; TA/GL1 can't consume them fast enough | Shared memory reduces VMEM FIFO pressure. | | | -> VMEM FIFO fills. | | +--------------------------+--------------------------------------------------------------------------------------------------+-------------------------------------------+ | utcl1_stall | Rapid page hopping (>32 pages) -> exceed UTCL1 entries -> in-flight stall. | Stay in one page. | +--------------------------+--------------------------------------------------------------------------------------------------+-------------------------------------------+ | ta_tcp_stall | Random access, TA waits for TCP. | Sequential access, TCP serves TA quickly. | +--------------------------+--------------------------------------------------------------------------------------------------+-------------------------------------------+
Note
Note: Above workloads are still WIP, the profiled result may not reflect the intended results.
Target Metrics
- gl2_backpressure:
TCP_TCR_TCP_STALL_CYCLES / tcp_busy - utcl1_stall:
TCP_UTCL1_STALL_INFLIGHT_MAX / tcp_busy
Build
hipcc -g <hip workload> -o <output>
# example: hipcc -g gl2_backpressure.hip -o gl2_backpressure
Profiling
# Note: --no-roof is optional and skips the
# benchmarking that is unrelated to the our purpose
# baseline profile
rocprof-compute profile -n gl2_backpressure_baseline --membw-analysis --no-roof -- ./gl2_backpressure
# optimized profile
rocprof-compute profile -n gl2_backpressure_optimized --membw-analysis --no-roof -- ./gl2_backpressure opt
Analyzing
# baseline profile
rocprof-compute analyze -p <path to profiled result> --membw-analysis