Re: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4]

[Ingo Molnar]

* Florian Schmidt <mista.tapas@xxxxxxx> wrote:

> and another one:
> 
> preemption latency trace v1.0.7 on 2.6.9-mm1-RT-V0.5.14-rt
> -------------------------------------------------------
>  latency: 225 us, entries: 36 (36)   |   [VP:0 KP:1 SP:1 HP:1 #CPUS:1]
>     -----------------
>     | task: jackd/1083, uid:1000 nice:0 policy:1 rt_prio:60
>     -----------------
>  => started at: try_to_wake_up+0x5a/0x110 <c01151ca>
>  => ended at:   finish_task_switch+0x31/0xc0 <c0115691>
> =======>
>   637 80000000 0.000ms (+0.000ms): (39) ((116))
>   637 80000000 0.000ms (+0.000ms): (1083) ((637))
>   637 80000000 0.000ms (+0.000ms): preempt_schedule (try_to_wake_up)
>   637 80000000 0.000ms (+0.000ms): preempt_schedule (__up_write)
>   637 00000000 0.000ms (+0.000ms): preempt_schedule (up_write_mutex)
>   637 80000000 0.000ms (+0.000ms): __schedule (preempt_schedule)
>   637 80000000 0.000ms (+0.000ms): profile_hit (__schedule)
>   637 80000000 0.000ms (+0.001ms): sched_clock (__schedule)
>  1083 80000000 0.002ms (+0.000ms): __switch_to (__schedule)
>  1083 80000000 0.002ms (+0.000ms): (637) ((1083))
>  1083 80000000 0.002ms (+0.000ms): (116) ((39))
>  1083 80000000 0.002ms (+0.000ms): finish_task_switch (__schedule)
>  1083 80000000 0.002ms (+0.000ms): trace_stop_sched_switched (finish_task_switch)
>  1083 80000000 0.002ms (+0.000ms): (1083) ((39))
>  1083 00000000 0.003ms (+0.000ms): bad_range (free_pages_bulk)
>  1083 00000000 0.003ms (+0.000ms): bad_range (free_pages_bulk)
>  1083 00000000 0.003ms (+0.000ms): _mutex_unlock_irqrestore (free_pages_bulk)
>  1083 00000000 0.003ms (+0.000ms): up_mutex (free_pages_bulk)
>  1083 00000000 0.004ms (+0.000ms): up_write_mutex (free_pages_bulk)
>  1083 00000000 0.004ms (+0.000ms): __up_write (up_write_mutex)
>  1083 80000000 0.004ms (+0.000ms): wake_up_process_mutex (__up_write)
>  1083 80000000 0.004ms (+0.000ms): try_to_wake_up (wake_up_process_mutex)
>  1083 80000000 0.004ms (+0.000ms): task_rq_lock (try_to_wake_up)
>  1083 80000000 0.004ms (+0.000ms): activate_task (try_to_wake_up)
>  1083 80000000 0.004ms (+0.000ms): sched_clock (activate_task)
>  1083 80000000 0.004ms (+0.000ms): recalc_task_prio (activate_task)
>  1083 80000000 0.004ms (+0.000ms): effective_prio (recalc_task_prio)
>  1083 80000000 0.004ms (+0.000ms): enqueue_task (activate_task)
>  1083 80000000 0.005ms (+0.000ms): (115) ((39))
>  1083 80000000 0.005ms (+0.006ms): (782) ((1083))
>  1083 00000000 0.011ms (+0.000ms): sys_gettimeofday (syscall_call)
>  1083 00000000 0.011ms (+0.000ms): user_trace_stop (sys_gettimeofday)
>  1083 80000000 0.012ms (+0.000ms): user_trace_stop (sys_gettimeofday)
>  1083 80000000 0.012ms (+0.000ms): update_max_trace (user_trace_stop)
>  1083 80000000 0.012ms (+0.000ms): _mmx_memcpy (update_max_trace)
>  1083 80000000 0.013ms (+0.000ms): kernel_fpu_begin (_mmx_memcpy)

should have mentioned that in the user-triggered modus you have to do
the latency measurement in userspace. It is only the trace that is
correct, for the time being. This trace shows what i'd expect a jackd
wakeup to look like normally: 13 usecs.

	Ingo
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