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    ftrace: latency tracer infrastructure · bc0c38d1
    Steven Rostedt authored
    
    
    This patch adds the latency tracer infrastructure. This patch
    does not add anything that will select and turn it on, but will
    be used by later patches.
    
    If it were to be compiled, it would add the following files
    to the debugfs:
    
     The root tracing directory:
    
      /debugfs/tracing/
    
    This patch also adds the following files:
    
      available_tracers
         list of available tracers. Currently no tracers are
         available. Looking into this file only shows
         "none" which is used to unregister all tracers.
    
      current_tracer
         The trace that is currently active. Empty on start up.
         To switch to a tracer simply echo one of the tracers that
         are listed in available_tracers:
    
       example: (used with later patches)
    
          echo function > /debugfs/tracing/current_tracer
    
         To disable the tracer:
    
           echo disable > /debugfs/tracing/current_tracer
    
      tracing_enabled
         echoing "1" into this file starts the ftrace function tracing
          (if sysctl kernel.ftrace_enabled=1)
         echoing "0" turns it off.
    
      latency_trace
          This file is readonly and holds the result of the trace.
    
      trace
          This file outputs a easier to read version of the trace.
    
      iter_ctrl
          Controls the way the output of traces look.
          So far there's two controls:
            echoing in "symonly" will only show the kallsyms variables
                without the addresses (if kallsyms was configured)
            echoing in "verbose" will change the output to show
                a lot more data, but not very easy to understand by
                humans.
            echoing in "nosymonly" turns off symonly.
            echoing in "noverbose" turns off verbose.
    
    Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
    Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@ghostprotocols.net>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    bc0c38d1