Show performance difference

perf diff command is used to displays the performance difference amongst two or more perf.data files captured via perf record command. If no input files provided, it will compare perf.data and perf.data.old by default. Check following example: 

  1. # perf diff
  2. # Event 'cycles:pp'
  3. #
  4. # Baseline  Delta Abs  Shared Object       Symbol
  5. # ........  .........  ..................  ..............................................
  6. #
  7.     20.49%     -0.28%  stream              [.] main._omp_fn.4
  8.     20.53%     -0.26%  stream              [.] main._omp_fn.5
  9.     24.62%     -0.25%  stream              [.] main._omp_fn.7
  10.      0.44%     -0.21%  [kernel.kallsyms]   [k] preempt_count_sub
  11.     24.70%     -0.20%  stream              [.] main._omp_fn.6
  12.      0.91%     -0.17%  stream              [.] main._omp_fn.2
  13.                +0.12%  [kernel.kallsyms]   [k] task_tick_fair
  14.                +0.09%  [kernel.kallsyms]   [k] perf_event_task_tick
  15.      0.01%     +0.08%  [kernel.kallsyms]   [k] sugov_should_update_freq
  16.      0.25%     +0.08%  [kernel.kallsyms]   [k] get_page_from_freelist
  17.     ......

Baseline is from perf.data.old, and perf diff only show events comparison result matching both specified files.