117
edits
Changes
→Parallelism
[[File:Effective-gpu.png|500px]]
Spin and Overhead Time
Spin time is the Wait time occurred when the CPU is busy. This often happens when a synchronization API causes the CPU to poll while the software thread is waiting. Overhead time is CPU time spent on the overhead of known synchronization and threading libraries, such as system synchronization APIs, Intel TBB, and OpenMP. This section lists the top functions in the application with the most spin and overhead time.
Bottom-Up Tab
The Bottom-up Tab enables us to investigate the concurrency problems in the application and time-dependent the performance of each thread. In the figure below in the lower half part of the window is the timeline view. As shown in brown colour which indicates the CPU time. Not until ~12 second, the mater thread was split into 8 threads and the first five were off-loaded, while the last threes (TID: 14500, 16268, 28576) were waiting (shown in light green colour) and the last two even waited all the way end which weakened parallelism. When brown band (CPU Time) concurrently happened to multiple threads, it means high level of parallelism.
[[File:Effective-CPU-Utilization-Histogram.png|500px]]
