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This new benchmark finds the total time that is taken to open, mmap,
enable, disable, munmap, close an evlist (time taken for new,
create_maps, config, delete is not counted in).

The evlist can be configured as in perf-record using the
-a,-C,-e,-u,--per-thread,-t,-p options.

The events can be duplicated in the evlist to quickly test performance
with many events using the -n options.

Furthermore, also the number of iterations used to calculate the
statistics is customizable.

Examples:
- Open one dummy event system-wide:

  $ sudo ./perf bench internals evlist-open-close
    Number of cpus:       4
    Number of threads:    1
    Number of events:     1 (4 fds)
    Number of iterations: 100
    Average open-close took: 613.870 usec (+- 32.852 usec)

- Open the group '{cs,cycles}' on CPU 0

  $ sudo ./perf bench internals evlist-open-close -e '{cs,cycles}' -C 0
    Number of cpus:       1
    Number of threads:    1
    Number of events:     2 (2...