NAME¶

dispatch_benchmark — Measures block execution time

SYNOPSIS¶

#include <dispatch/dispatch.h>

uint64_t
dispatch_benchmark(size_t count, void (^block)(void));

uint64_t
dispatch_benchmark_f(size_t count, void *context, void (*function)(void *));

DESCRIPTION¶

The dispatch_benchmark() function executes the given block multiple times according to the count variable and then returns the average number of nanoseconds per execution. This function is for debugging and performance analysis work. For the best results, pass a high count value to dispatch_benchmark(). When benchmarking concurrent code, please compare the serial version of the code against the concurrent version, and compare the concurrent version on different classes of hardware. Please look for inflection points with various data sets and keep the following facts in mind:

• Code bound by computational bandwidth may be inferred by proportional changes in performance as concurrency is increased.
• Code bound by memory bandwidth may be inferred by negligible changes in performance as concurrency is increased.
• Code bound by critical sections may be inferred by retrograde changes in performance as concurrency is increased.
  • Intentional: locks, mutexes, and condition variables.
  • Accidental: unrelated and frequently modified data on the same cache-line.

RETURN VALUE¶

The dispatch_benchmark() function returns the average number of nanoseconds the given block takes to execute.

SEE ALSO¶

dispatch(3)