User Guide

Contents

View Performance Inefficiencies of Data-parallel Constructs

The
Statistics Tab
also contains the efficiency information for each parallel construct if they are employed by the algorithm. This data will show up under the
Parallel Efficiency
tab in the
Statistics
group.
The data parallel construct efficiency for each instance of a kernel. The column provides information that is useful for understanding the execution, and makes inferences to improve performance.
  • The parallel algorithms are nested under the kernel name when the kernel name can be demangled correctly.
  • The Efficiency column indicates the efficiency of the algorithm, when associated with the algorithm name. For the participating worker threads, the efficiency column indicates the efficiency of the thread while participating in the execution. This data is typically derived from the total time spent on the parallel construct and the time the thread spent participating in other parallel constructs.
  • Task Count column indicates the number of tasks executed by the participating thread.
  • Duration indicates the time the participating thread spends executing tasks from the parallel construct.
  • CPU time is the
    Duration
    column data expressed as a percentage of the wall clock time of the parallel construct.
  • Other Time
    will be 0 if the thread fully participates in the execution of tasks from the parallel construct. However, in runtimes such as Threading Building Block (TBB), the participating threads may steal tasks from other parallel constructs submitted to the device to provide better dynamic load balancing and throughput. In such cases, the
    Other Time
    column will indicate the percentage of the total wall clock time the participating thread spends executing tasks from other parallel constructs.
  • Fork Imbalance
    indicates the penalty for waking up threads to participate in the execution of tasks from the parallel construct. For more information, see Startup Penalty.
  • Join Imbalance
    indicates the degree of imbalanced execution of tasks from the parallel constructs by the participating worker threads. For more information, see Data Parallel Efficiency.

Product and Performance Information

1

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Notice revision #20110804