Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm1-V0.7.27-3

[Florian Schmidt]

On Tue, 16 Nov 2004 22:20:39 +0100
Florian Schmidt <mista.tapas@xxxxxxx> wrote:

> /proc/latency_trace doesn't show that high latencies either on console
> switch:
> 

correction: now i do see large wakeup latencies in /proc/latency_trace, but
only when rtc_wakeup is not running [??? :)]. something's fishy..

(IRQ 1/18/CPU#0): new 2 us maximum-latency wakeup.
(IRQ 1/18/CPU#0): new 3 us maximum-latency wakeup.
(syslogd/302/CPU#0): new 4 us maximum-latency wakeup.
(ksoftirqd/0/3/CPU#0): new 4 us maximum-latency wakeup.
(ksoftirqd/0/3/CPU#0): new 5 us maximum-latency wakeup.
(IRQ 0/2/CPU#0): new 857 us maximum-latency wakeup.
(IRQ 0/2/CPU#0): new 891 us maximum-latency wakeup.
(IRQ 0/2/CPU#0): new 976 us maximum-latency wakeup.
(IRQ 0/2/CPU#0): new 1117 us maximum-latency wakeup.

It seems this excerpt from below trace is characteristic for all the long
traces:

   5 80000002 0.001ms (+1.114ms): __do_softirq (do_softirq)
   5 00000000 1.115ms (+0.000ms): preempt_schedule (_mmx_memcpy)

preemption latency trace v1.0.7 on 2.6.10-rc2-mm1-RT-V0.7.27-10
-------------------------------------------------------
 latency: 1117 us, entries: 22 (22)   |   [VP:0 KP:1 SP:1 HP:1 #CPUS:1]
    -----------------
    | task: IRQ 0/2, uid:0 nice:0 policy:1 rt_prio:50
    -----------------
 => started at: try_to_wake_up+0x51/0x170 <c010f3a1>
 => ended at:   finish_task_switch+0x51/0xb0 <c010f911>
=======>
    5 80010004 0.000ms (+0.000ms): trace_start_sched_wakeup (try_to_wake_up)
    5 80010003 0.000ms (+0.000ms): (49) ((98))
    5 80010003 0.000ms (+0.000ms): (2) ((5))
    5 80010003 0.000ms (+0.000ms): try_to_wake_up (wake_up_process)
    5 80010003 0.000ms (+0.000ms): (0) ((1))
    5 80010002 0.000ms (+0.000ms): preempt_schedule (try_to_wake_up)
    5 80010002 0.000ms (+0.000ms): wake_up_process (redirect_hardirq)
    5 80010001 0.000ms (+0.000ms): preempt_schedule (__do_IRQ)
    5 80010001 0.000ms (+0.000ms): irq_exit (do_IRQ)
    5 80000002 0.000ms (+0.000ms): do_softirq (irq_exit)
    5 80000002 0.001ms (+1.114ms): __do_softirq (do_softirq)
    5 00000000 1.115ms (+0.000ms): preempt_schedule (_mmx_memcpy)
    5 90000000 1.115ms (+0.000ms): __schedule (preempt_schedule)
    5 90000000 1.115ms (+0.000ms): profile_hit (__schedule)
    5 90000001 1.116ms (+0.000ms): sched_clock (__schedule)
    2 80000002 1.116ms (+0.000ms): __switch_to (__schedule)
    2 80000002 1.116ms (+0.000ms): (5) ((2))
    2 80000002 1.116ms (+0.000ms): (98) ((49))
    2 80000002 1.116ms (+0.000ms): finish_task_switch (__schedule)
    2 80000001 1.116ms (+0.000ms): trace_stop_sched_switched (finish_task_switch)
    2 80000001 1.116ms (+0.003ms): (2) ((49))
    2 80000001 1.120ms (+0.000ms): trace_stop_sched_switched (finish_task_switch)

Ah, and one more thing: When i boot up the computer my init script sets irq
3 to prio 98. But it seems the irq handler's priority changes actually when
the soundcard is used the first time. So i need to re-set the irq prio
_after_ i have  used the soundcard for the first time..

flo
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