• Steven Rostedt's avatar
    ftrace: tracer for scheduler wakeup latency · 352ad25a
    Steven Rostedt authored
    
    
    This patch adds the tracer that tracks the wakeup latency of the
    highest priority waking task.
    
      "wakeup" is added to /debugfs/tracing/available_tracers
    
    Also added to /debugfs/tracing
    
      tracing_max_latency
         holds the current max latency for the wakeup
    
      wakeup_thresh
         if set to other than zero, a log will be recorded
         for every wakeup that takes longer than the number
         entered in here (usecs for all counters)
         (deletes previous trace)
    
    Examples:
    
      (with ftrace_enabled = 0)
    
    ============
    preemption latency trace v1.1.5 on 2.6.24-rc8
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    --------------------------------------------------------------------
     latency: 26 us, #2/2, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
        -----------------
        | task: migration/0-3 (uid:0 nice:-5 policy:1 rt_prio:99)
        -----------------
    
                     _------=> CPU#
                    / _-----=> irqs-off
                   | / _----=> need-resched
                   || / _---=> hardirq/softirq
                   ||| / _--=> preempt-depth
                   |||| /
                   |||||     delay
       cmd     pid ||||| time  |   caller
          \   /    |||||   \   |   /
       quilt-8551  0d..3    0us+: wake_up_process+0x15/0x17 <ffffffff80233e80> (sched_exec+0xc9/0x100 <ffffffff80235343>)
       quilt-8551  0d..4   26us : sched_switch_callback+0x73/0x81 <ffffffff80338d2f> (schedule+0x483/0x6d5 <ffffffff8048b3ee>)
    
    vim:ft=help
    ============
    
      (with ftrace_enabled = 1)
    
    ============
    preemption latency trace v1.1.5 on 2.6.24-rc8
    --------------------------------------------------------------------
     latency: 36 us, #45/45, CPU#0 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
        -----------------
        | task: migration/1-5 (uid:0 nice:-5 policy:1 rt_prio:99)
        -----------------
    
                     _------=> CPU#
                    / _-----=> irqs-off
                   | / _----=> need-resched
                   || / _---=> hardirq/softirq
                   ||| / _--=> preempt-depth
                   |||| /
                   |||||     delay
       cmd     pid ||||| time  |   caller
          \   /    |||||   \   |   /
        bash-10653 1d..3    0us : wake_up_process+0x15/0x17 <ffffffff80233e80> (sched_exec+0xc9/0x100 <ffffffff80235343>)
        bash-10653 1d..3    1us : try_to_wake_up+0x271/0x2e7 <ffffffff80233dcf> (sub_preempt_count+0xc/0x7a <ffffffff8023309e>)
        bash-10653 1d..2    2us : try_to_wake_up+0x296/0x2e7 <ffffffff80233df4> (update_rq_clock+0x9/0x20 <ffffffff802303f3>)
        bash-10653 1d..2    2us : update_rq_clock+0x1e/0x20 <ffffffff80230408> (__update_rq_clock+0xc/0x90 <ffffffff80230366>)
        bash-10653 1d..2    3us : __update_rq_clock+0x1b/0x90 <ffffffff80230375> (sched_clock+0x9/0x29 <ffffffff80214529>)
        bash-10653 1d..2    4us : try_to_wake_up+0x2a6/0x2e7 <ffffffff80233e04> (activate_task+0xc/0x3f <ffffffff8022ffca>)
        bash-10653 1d..2    4us : activate_task+0x2d/0x3f <ffffffff8022ffeb> (enqueue_task+0xe/0x66 <ffffffff8022ff66>)
        bash-10653 1d..2    5us : enqueue_task+0x5b/0x66 <ffffffff8022ffb3> (enqueue_task_rt+0x9/0x3c <ffffffff80233351>)
        bash-10653 1d..2    6us : try_to_wake_up+0x2ba/0x2e7 <ffffffff80233e18> (check_preempt_wakeup+0x12/0x99 <ffffffff80234f84>)
    [...]
        bash-10653 1d..5   33us : tracing_record_cmdline+0xcf/0xd4 <ffffffff80338aad> (_spin_unlock+0x9/0x33 <ffffffff8048d3ec>)
        bash-10653 1d..5   34us : _spin_unlock+0x19/0x33 <ffffffff8048d3fc> (sub_preempt_count+0xc/0x7a <ffffffff8023309e>)
        bash-10653 1d..4   35us : wakeup_sched_switch+0x65/0x2ff <ffffffff80339f66> (_spin_lock_irqsave+0xc/0xa9 <ffffffff8048d08b>)
        bash-10653 1d..4   35us : _spin_lock_irqsave+0x19/0xa9 <ffffffff8048d098> (add_preempt_count+0xe/0x77 <ffffffff8023311a>)
        bash-10653 1d..4   36us : sched_switch_callback+0x73/0x81 <ffffffff80338d2f> (schedule+0x483/0x6d5 <ffffffff8048b3ee>)
    
    vim:ft=help
    ============
    
    The [...] was added here to not waste your email box space.
    Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    352ad25a
ftrace.h 1.68 KB