[Tuning] Disable CPU Idle in NNAPI workload with PMQoS CPU DMA Latency
To improve the return path latency, we want to keep the CPU at at least WFI state (Idle_1). The PMQos cpu_dma_latency knob prevents the CPU from falling below WFI state. This makes the return path CPU wakeup latency very good. Check with wvw@, the power impact shouldn't be too significant.
The average energy cost per inference dropped from 3.85 to 3.47 mJ. The reason why the power number is lower WITH disable-idle is that, due to better latency, we get to run more inferences given the same amount of time. This makes the average power consumption lower.
Measurement:
MLPerf IC model Latency (ms) Power (mW) Energy/inference (mJ) MLPerf scores
Default 1.35 2837 3.85 560
Disable CPU Idle 0.98 3539 3.47 826
https://docs.google.com/presentation/d/1zx7sLkhOClmuRTCrq8-l3N1mZrrv7f-CtcdMuzV0eaI/edit?pli=1#slide=id.g12dd9e50b4b_0_0
Bug: 232183574
Test: MLPerf on Android T. Performance improved. Verified on Perfetto.
Change-Id: If067e0851bea0475043ef2127a25ed3a5fdab093
2 files changed