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    ftrace: CPU buffer start annotation clean ups · 12ef7d44
    Steven Rostedt 提交于
    Impact: better handling of CPU buffer start annotation
    
    Because of the confusion with the per CPU buffers wrapping where
    one CPU might be more active at the end of the trace than the other
    CPUs causing that one CPU to have a shorter history. Kernel
    developers were confused by the "missing" data of that one CPU
    at the beginning of the trace output. An annotation was added to
    the trace output to show that the buffer had started:
    
     # tracer: function
     #
     #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
     #              | |       |          |         |
     ##### CPU 3 buffer started ####
              <idle>-0     [003]   158.192959: smp_apic_timer_interrupt
     [...]
               <idle>-0     [003]   161.556520: default_idle
     ##### CPU 1 buffer started ####
               <idle>-0     [001]   161.592494: hrtimer_force_reprogram
     [etc]
    
    But this annotation gets a bit messy when tracers do not fill the
    buffers. This patch does a couple of things:
    
     One) it adds a flag to trace_options to disable these annotations
    
     Two) it does not annotate if the tracer did not overflow its buffer.
    
    This makes the output much cleaner.
    Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
    Signed-off-by: NIngo Molnar <mingo@elte.hu>
    12ef7d44
trace.h 15.1 KB