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    SubjectRe: Realtime Preemption, 2.6.12, Beginners Guide?
    Date
    On Wednesday 06 Jul 2005 17:37, Alistair John Strachan wrote:
    [big snip]
    > >
    > > could you try the patch below (or the -51-05 patch that i just
    > > uploaded), does it fix this latency?
    > >
    > > Ingo
    >
    > I'm beginning to understand the issue, and I see why you think the proposed
    > patch fixes it. I'll compile and boot V0.7.51-05 now.

    Indeed, this seems to have fixed it.

    ( softirq-timer/0-3 |#0): new 8 us maximum-latency wakeup.
    ( softirq-timer/0-3 |#0): new 9 us maximum-latency wakeup.
    ( softirq-timer/0-3 |#0): new 9 us maximum-latency wakeup.
    ( softirq-timer/0-3 |#0): new 9 us maximum-latency wakeup.
    ( softirq-timer/0-3 |#0): new 10 us maximum-latency wakeup.
    ( softirq-timer/0-3 |#0): new 14 us maximum-latency wakeup.

    Find attached another trace (only 33us this time).

    --
    Cheers,
    Alistair.

    personal: alistair()devzero!co!uk
    university: s0348365()sms!ed!ac!uk
    student: CS/CSim Undergraduate
    contact: 1F2 55 South Clerk Street,
    Edinburgh. EH8 9PP.
    preemption latency trace v1.1.4 on 2.6.12-RT-V0.7.51-05
    --------------------------------------------------------------------
    latency: 38 us, #27/27, CPU#0 | (M:rt VP:0, KP:1, SP:1 HP:1 #P:1)
    -----------------
    | task: softirq-timer/0-3 (uid:0 nice:-10 policy:0 rt_prio:0)
    -----------------

    _------=> CPU#
    / _-----=> irqs-off
    | / _----=> need-resched
    || / _---=> hardirq/softirq
    ||| / _--=> preempt-depth
    |||| /
    ||||| delay
    cmd pid ||||| time | caller
    \ / ||||| \ | /
    <...>-3485 0dnh3 0us!: <6f6f726b> (<616d6974>)
    <...>-3485 0dnh3 1us : __trace_start_sched_wakeup (try_to_wake_up)
    <...>-3485 0dnh3 1us : __trace_start_sched_wakeup <softirq--3> (69 0)
    <...>-3485 0dnh2 2us : try_to_wake_up <softirq--3> (69 76)
    <...>-3485 0dnh1 2us : preempt_schedule (try_to_wake_up)
    <...>-3485 0dnh1 3us : wake_up_process (trigger_softirqs)
    <...>-3485 0dnh1 3us : local_irq_restore (do_softirq)
    <...>-3485 0Dnh1 4us+: preempt_schedule (do_softirq)
    <...>-3485 0Dnh. 7us : __schedule (work_resched)
    <...>-3485 0Dnh. 8us : profile_hit (__schedule)
    <...>-3485 0Dnh1 8us+: sched_clock (__schedule)
    <...>-3485 0Dnh2 12us : dequeue_task (__schedule)
    <...>-3485 0Dnh2 13us : recalc_task_prio (__schedule)
    <...>-3485 0Dnh2 13us : effective_prio (recalc_task_prio)
    <...>-3485 0Dnh2 13us : enqueue_task (__schedule)
    <...>-3485 0Dnh2 14us+: trace_array (__schedule)
    <...>-3485 0Dnh2 18us : trace_array <softirq--3> (69 6e)
    <...>-3485 0Dnh2 18us : trace_array <<...>-3485> (76 78)
    <...>-3485 0Dnh2 20us+: trace_array (__schedule)
    softirq--3 0Dnh2 28us+: __switch_to (__schedule)
    softirq--3 0Dnh2 31us : __schedule <<...>-3485> (76 69)
    softirq--3 0Dnh2 31us : finish_task_switch (__schedule)
    softirq--3 0Dnh1 32us : trace_stop_sched_switched (finish_task_switch)
    softirq--3 0Dnh2 33us+: trace_stop_sched_switched <softirq--3> (69 0)
    softirq--3 0Dnh2 35us : trace_stop_sched_switched (finish_task_switch)


    vim:ft=help
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