• Steven Rostedt's avatar
    tracing: add function profiler · bac429f0
    Steven Rostedt authored
    
    
    Impact: new profiling feature
    
    This patch adds a function profiler. In debugfs/tracing/ two new
    files are created.
    
      function_profile_enabled  - to enable or disable profiling
    
      trace_stat/functions   - the profiled functions.
    
    For example:
    
      echo 1 > /debugfs/tracing/function_profile_enabled
      ./hackbench 50
      echo 0 > /debugfs/tracing/function_profile_enabled
    
    yields:
    
      cat /debugfs/tracing/trace_stat/functions
    
      Function                               Hit
      --------                               ---
      _spin_lock                        10106442
      _spin_unlock                      10097492
      kfree                              6013704
      _spin_unlock_irqrestore            4423941
      _spin_lock_irqsave                 4406825
      __phys_addr                        4181686
      __slab_free                        4038222
      dput                               4030130
      path_put                           4023387
      unroll_tree_refs                   4019532
    [...]
    
    The most hit functions are listed first. Functions that are not
    hit are not listed.
    
    This feature depends on and uses dynamic function tracing. When the
    function profiling is disabled, no overhead occurs. But it still
    takes up around 300KB to hold the data, thus it is not recomended
    to keep it enabled for systems low on memory.
    
    When a '1' is echoed into the function_profile_enabled file, the
    counters for is function is reset back to zero. Thus you can see what
    functions are hit most by different programs.
    Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
    bac429f0
ftrace.h 14.9 KB