Re: 2.6.17-rt1

From: Lee Revell
Date: Wed Jun 21 2006 - 20:56:04 EST


On Sun, 2006-06-18 at 09:06 +0200, Ingo Molnar wrote:
> i have released the 2.6.17-rt1 tree, which can be downloaded from the
> usual place:
>
> http://redhat.com/~mingo/realtime-preempt/
>
> this is a fixes-only release: merged to 2.6.17-final and smaller fixes.
>
> to build a 2.6.17-rc6-rt1 tree, the following patches should be applied:
>
> http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.17.tar.bz2
> http://redhat.com/~mingo/realtime-preempt/patch-2.6.17-rt1

I'm getting some strange latency tracer output on a dual core AMD box.
Why does it start at 404us?

Lee

preemption latency trace v1.1.5 on 2.6.17-rt1-smp-latency-trace
--------------------------------------------------------------------
latency: 415 us, #26/26, CPU#1 | (M:rt VP:0, KP:0, SP:1 HP:1 #P:2)
-----------------
| task: kjournald-2043 (uid:0 nice:-5 policy:0 rt_prio:0)
-----------------

_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
<idle>-0 1Dn.1 404us : smp_reschedule_interrupt (reschedule_interrupt)
<idle>-0 1.n.1 405us : __exit_idle (cpu_idle)
<idle>-0 1.n.1 405us : atomic_notifier_call_chain (__exit_idle)
<idle>-0 1.n.1 406us : rcu_read_lock (atomic_notifier_call_chain)
<idle>-0 1Dn.1 406us : rcu_read_lock (0 0 badc)
<idle>-0 1Dn.1 406us : rcu_read_lock (ffff810002eb7228 0 badc)
<idle>-0 1.n.1 406us : rcu_read_unlock (atomic_notifier_call_chain)
<idle>-0 1Dn.1 407us : rcu_read_unlock (ffff810002eb7228 0 1)
<idle>-0 1Dn.1 407us : rcu_read_unlock (0 0 0)
<idle>-0 1Dn.. 407us : __schedule (cpu_idle)
<idle>-0 1Dn.. 407us : profile_hit (__schedule)
<idle>-0 1Dn.1 408us : sched_clock (__schedule)
<idle>-0 1Dn.1 408us : _raw_spin_lock_irq (__schedule)
<idle>-0 1Dn.2 409us : recalc_task_prio (__schedule)
<idle>-0 1Dn.2 410us : effective_prio (recalc_task_prio)
<idle>-0 1Dn.2 410us : effective_prio <<...>-2043> (-10 -10)
<idle>-0 1D..2 412us : __switch_to (thread_return)
<...>-2043 1D..2 413us : thread_return <<idle>-0> (20 -10)
<...>-2043 1D..2 413us : _raw_spin_unlock_irq (thread_return)
<...>-2043 1...1 413us : constant_test_bit (_raw_spin_unlock_irq)
<...>-2043 1...1 413us : trace_stop_sched_switched (thread_return)
<...>-2043 1D..1 414us : _raw_spin_lock (trace_stop_sched_switched)
<...>-2043 1D..2 414us : trace_stop_sched_switched <<...>-2043> (110 1)
<...>-2043 1D..2 415us : thread_return (thread_return)



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