Ingo Molnar wrote:
add 'notrace' to the definition of read_tsc in arch/i386/kernel/tsc.c
OK.
(or do echo 1 > /proc/sys/kernel/trace_use_raw_cycles
if you are using recent enough -rt)
Is patch-2.6.20-rt8 recent enough?
# ./trace-it 1 >trace
# cat trace
preemption latency trace v1.1.5 on 2.6.20.7-rt8
--------------------------------------------------------------------
latency: 1000034 us, #10083/10083, CPU#0 | (M:rt VP:0, KP:0, SP:1 HP:1)
-----------------
| task: trace-it-939 (uid:0 nice:0 policy:0 rt_prio:0)
-----------------
_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
trace-it-939 0D... 0us : user_trace_start (sys_prctl)
trace-it-939 0.... 0us : rt_up (user_trace_start)
trace-it-939 0...1 1us : rt_mutex_unlock (rt_up)
trace-it-939 0D... 1us+< (0)
trace-it-939 0.... 4us > sys_rt_sigprocmask (00000000 bfadff4c
000000d8)
trace-it-939 0.... 5us : sys_rt_sigprocmask (sysenter_past_esp)
trace-it-939 0.... 5us : copy_from_user (sys_rt_sigprocmask)
trace-it-939 0.... 5us : __copy_from_user_ll (copy_from_user)
trace-it-939 0.... 5us : sigprocmask (sys_rt_sigprocmask)
trace-it-939 0.... 5us : __lock_text_start (sigprocmask)
trace-it-939 0.... 6us : recalc_sigpending (sigprocmask)
[...]
<idle>-0 0DN.. 1000027us : __sched_text_start (cpu_idle)
<idle>-0 0DN.1 1000027us : __sched_text_start (c0100f30 0 0)
<idle>-0 0DN.1 1000027us : sched_clock (__sched_text_start)
<idle>-0 0D..2 1000028us : __switch_to (__sched_text_start)
trace-it-939 0D..2 1000028us : __sched_text_start <<idle>-0> (20 -2)
trace-it-939 0D..1 1000029us : trace_stop_sched_switched
(__sched_text_start)
trace-it-939 0.... 1000029us : hrtimer_cancel (do_nanosleep)
trace-it-939 0.... 1000030us : hrtimer_try_to_cancel (hrtimer_cancel)
trace-it-939 0D... 1000031us < (0)
trace-it-939 0.... 1000032us > sys_prctl (00000000 00000000 000000d8)
trace-it-939 0.... 1000032us : sys_prctl (sysenter_past_esp)
trace-it-939 0.... 1000032us : user_trace_stop (sys_prctl)
trace-it-939 0D... 1000033us : user_trace_stop (sys_prctl)
This looks better.
I will let my test program run overnight.
Regards.
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