LWN.net Ftrace Articles by Steven Rostedt

LWN.net Ftrace Articles by Steven Rostedt

• Debugging the kernel using Ftrace - part 1
• Debugging the kernel using Ftrace - part 2
• Secrets of the Ftrace function tracer

 Ever wanted to see what functions are called in a running Linux kernel?

  

    [tracing]# cd /sys/kernel/debug/tracing

    [tracing]# echo function_graph > current_tracer 

    [tracing]# cat trace | head -20

    # tracer: function_graph

    #

    # CPU  DURATION                  FUNCTION CALLS

    # |     |   |                     |   |   |   |

     1)   1.015 us    |        _spin_lock_irqsave();

     1)   0.476 us    |        internal_add_timer();

     1)   0.423 us    |        wake_up_idle_cpu();

     1)   0.461 us    |        _spin_unlock_irqrestore();

     1)   4.770 us    |      }

     1)   5.725 us    |    }

     1)   0.450 us    |    mutex_unlock();

     1) + 24.243 us   |  }

     1)   0.483 us    |  _spin_lock_irq();

     1)   0.517 us    |  _spin_unlock_irq();

     1)               |  prepare_to_wait() {

     1)   0.468 us    |    _spin_lock_irqsave();

     1)   0.502 us    |    _spin_unlock_irqrestore();

     1)   2.411 us    |  }

     1)   0.449 us    |  kthread_should_stop();

     1)               |  schedule() {