Lee Revell <rlrevell@xxxxxxxxxxx> writes:
> Did you ever try the latency tracer? (See LKML archives for
> instructions)
Yes I did (this time better than 2 or 3 days ago :-/ ).
- I compiled and booted 2.6.28-rt5 with latency tracer enabled
- I verified that I got latency trace enabled (seen trace in kern.log)
I only got some traces after running this (detail added for the sake
of other newbies like me) :
gandalf:/proc/sys/kernel# echo 0 > preempt_max_latency
Here's the max latency trace I got (note that I got a similar trace
*before* running the test, so I'd say it's unrelated to the AC3
drop-out problem.):
preemption latency trace v1.1.5 on 2.6.18-rt5
--------------------------------------------------------------------
latency: 19 us, #58/58, CPU#0 | (M:rt VP:0, KP:0, SP:1 HP:1)
-----------------
| task: posix_cpu_timer-2 (uid:0 nice:0 policy:1 rt_prio:99)
-----------------
_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
<idle>-0 0Dnh2 0us : __trace_start_sched_wakeup (try_to_wake_up)
<idle>-0 0Dnh2 0us : __trace_start_sched_wakeup <<...>-2> (0 0)
<idle>-0 0Dnh2 0us : try_to_wake_up <<...>-2> (199 20)
<idle>-0 0Dnh1 0us : preempt_schedule (try_to_wake_up)
<idle>-0 0Dnh1 0us : wake_up_process (run_posix_cpu_timers)
<idle>-0 0Dnh1 0us : note_interrupt (handle_level_irq)
<idle>-0 0Dnh2 0us : enable_8259A_irq (handle_level_irq)
<idle>-0 0Dnh2 1us : preempt_schedule (enable_8259A_irq)
<idle>-0 0Dnh1 1us : preempt_schedule (handle_level_irq)
<idle>-0 0Dnh1 2us : irq_exit (do_IRQ)
<idle>-0 0Dnh1 3us : do_IRQ (b0101ade b 0)
<idle>-0 0Dnh1 3us : handle_level_irq (do_IRQ)
<idle>-0 0Dnh2 3us+: mask_and_ack_8259A (handle_level_irq)
<idle>-0 0Dnh2 8us : preempt_schedule (mask_and_ack_8259A)
<idle>-0 0Dnh2 8us : redirect_hardirq (handle_level_irq)
<idle>-0 0Dnh2 9us : wake_up_process (redirect_hardirq)
<idle>-0 0Dnh2 9us : try_to_wake_up (wake_up_process)
<idle>-0 0Dnh2 9us : task_rq_lock (try_to_wake_up)
<idle>-0 0Dnh3 9us : activate_task (try_to_wake_up)
<idle>-0 0Dnh3 9us : sched_clock (activate_task)
<idle>-0 0Dnh3 9us : __activate_task (activate_task)
<idle>-0 0Dnh3 9us : __activate_task <<...>-2006> (59 1)
<idle>-0 0Dnh3 9us : enqueue_task (__activate_task)
<idle>-0 0Dnh3 9us : __trace_start_sched_wakeup (try_to_wake_up)
<idle>-0 0Dnh3 9us : try_to_wake_up <<...>-2006> (140 20)
<idle>-0 0Dnh2 9us : preempt_schedule (try_to_wake_up)
<idle>-0 0Dnh2 9us : wake_up_process (redirect_hardirq)
<idle>-0 0Dnh1 10us : preempt_schedule (handle_level_irq)
<idle>-0 0Dnh1 10us : irq_exit (do_IRQ)
<idle>-0 0Dnh1 11us : do_IRQ (b0101ade e 0)
<idle>-0 0Dnh1 11us : handle_level_irq (do_IRQ)
<idle>-0 0Dnh2 11us+: mask_and_ack_8259A (handle_level_irq)
<idle>-0 0Dnh2 16us : preempt_schedule (mask_and_ack_8259A)
<idle>-0 0Dnh2 16us : redirect_hardirq (handle_level_irq)
<idle>-0 0Dnh2 16us : wake_up_process (redirect_hardirq)
<idle>-0 0Dnh2 16us : try_to_wake_up (wake_up_process)
<idle>-0 0Dnh2 16us : task_rq_lock (try_to_wake_up)
<idle>-0 0Dnh3 17us : activate_task (try_to_wake_up)
<idle>-0 0Dnh3 17us : sched_clock (activate_task)
<idle>-0 0Dnh3 17us : __activate_task (activate_task)
<idle>-0 0Dnh3 17us : __activate_task <<...>-861> (53 2)
<idle>-0 0Dnh3 17us : enqueue_task (__activate_task)
<idle>-0 0Dnh3 17us : __trace_start_sched_wakeup (try_to_wake_up)
<idle>-0 0Dnh3 17us : try_to_wake_up <<...>-861> (146 20)
<idle>-0 0Dnh2 17us : preempt_schedule (try_to_wake_up)
<idle>-0 0Dnh2 17us : wake_up_process (redirect_hardirq)
<idle>-0 0Dnh1 17us : preempt_schedule (handle_level_irq)
<idle>-0 0Dnh1 17us : irq_exit (do_IRQ)
<idle>-0 0Dn.. 17us : __schedule (cpu_idle)
<idle>-0 0Dn.. 17us : profile_hit (__schedule)
<idle>-0 0Dn.1 18us : sched_clock (__schedule)
<...>-2 0D..2 18us : __switch_to (__schedule)
<...>-2 0D..2 18us : __schedule <<idle>-0> (20 199)
<...>-2 0...1 18us : trace_stop_sched_switched (__schedule)
<...>-2 0D..1 18us : trace_stop_sched_switched <<...>-2> (0 0)
<...>-2 0D..2 18us : __schedule (__schedule)
vim:ft=help
Cheers
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