Dear Rostedt,
This is chensong who was asking question in #linux-rt channel. I
upgrated my rt-tests to the lastest version (cyclictest V 1.80) and
trace-cmd as well(trace-cmd version 2.9.dev).
I ran commands like these:
trace-cmd start -e irq -e sched -e timer -p function -l '*spin*';
cyclictest -p 90 -m -c 0 -i 100 -h 100 -q -l 1000000 -b 80 --tracemark
trace-cmd extract
trace-cmd report
The log of last cycle before cyclictest reached the threshold and quit
is like that:
<idle>-0 [000] 130.330659: irq_handler_entry: irq=4 name=arch_timer
<idle>-0 [000] 130.330665: function:
_raw_spin_lock_irqsave
<idle>-0 [000] 130.330666: hrtimer_cancel:
hrtimer=0xffffff801234bdc8
<idle>-0 [000] 130.330667: function:
_raw_spin_unlock_irqrestore
<idle>-0 [000] 130.330668: hrtimer_expire_entry:
hrtimer=0xffffff801234bdc8 now=130207149982 function=hrtimer_wakeup/0x0
<idle>-0 [000] 130.330669: function:
_raw_spin_lock_irqsave
<idle>-0 [000] 130.330682: sched_waking: comm=cyclictest
pid=1720 prio=9 target_cpu=000
<idle>-0 [000] 130.330695: function: _raw_spin_lock
<idle>-0 [000] 130.330697: function: _raw_spin_lock
<idle>-0 [000] 130.330699: sched_wakeup: cyclictest:1720
[9] success=1 CPU:000
<idle>-0 [000] 130.330699: function:
_raw_spin_unlock_irqrestore
<idle>-0 [000] 130.330700: hrtimer_expire_exit:
hrtimer=0xffffff801234bdc8
<idle>-0 [000] 130.330701: function: _raw_spin_lock_irq
<idle>-0 [000] 130.330702: function:
_raw_spin_unlock_irqrestore
<idle>-0 [000] 130.330703: irq_handler_exit: irq=4 ret=handled
It took 44us from irq_handler_entry to irq_handler_exit, compare to
normal case which generally took only around 15us, it produced around
30us extra latency. I also found something wrong like
"_raw_spin_lock_irqsave from 130.330669 to 130.330682" and "sched_waking
from 130.330682 to 130.330695".
PS: cyclictest was running on CPU0 and a firefox was running on CPU1
meanwhile.
I tried to dig deeper, is there any way to find more information, please
let me know, many thanks.
Here is more log for reference:
<idle>-0 [000] 130.330659: irq_handler_entry: irq=4 name=arch_timer
<idle>-0 [000] 130.330665: function:
_raw_spin_lock_irqsave
<idle>-0 [000] 130.330666: hrtimer_cancel:
hrtimer=0xffffff801234bdc8
<idle>-0 [000] 130.330667: function:
_raw_spin_unlock_irqrestore
<idle>-0 [000] 130.330668: hrtimer_expire_entry:
hrtimer=0xffffff801234bdc8 now=130207149982 function=hrtimer_wakeup/0x0
<idle>-0 [000] 130.330669: function:
_raw_spin_lock_irqsave
<idle>-0 [000] 130.330682: sched_waking:
comm=cyclictest pid=1720 prio=9 target_cpu=000
<idle>-0 [000] 130.330695: function:
_raw_spin_lock
<idle>-0 [000] 130.330697: function:
_raw_spin_lock
<idle>-0 [000] 130.330699: sched_wakeup:
cyclictest:1720 [9] success=1 CPU:000
<idle>-0 [000] 130.330699: function:
_raw_spin_unlock_irqrestore
<idle>-0 [000] 130.330700: hrtimer_expire_exit:
hrtimer=0xffffff801234bdc8
<idle>-0 [000] 130.330701: function:
_raw_spin_lock_irq
<idle>-0 [000] 130.330702: function:
_raw_spin_unlock_irqrestore
<idle>-0 [000] 130.330703: irq_handler_exit: irq=4
ret=handled
firefox-1722 [001] 130.330705: function:
_raw_spin_lock_irqsave
<idle>-0 [000] 130.330706: function:
_raw_spin_lock_irqsave
<idle>-0 [000] 130.330706: hrtimer_cancel:
hrtimer=0xffffffc07ffbe960
firefox-1722 [001] 130.330706: function:
_raw_spin_lock
firefox-1722 [001] 130.330707: function:
_raw_spin_unlock_irqrestore
<idle>-0 [000] 130.330708: function:
_raw_spin_unlock_irqrestore
firefox-1722 [001] 130.330708: function:
rt_spin_lock
<idle>-0 [000] 130.330709: function:
_raw_spin_lock_irqsave
<idle>-0 [000] 130.330709: hrtimer_start:
hrtimer=0xffffffc07ffbe960 function=tick_sched_timer/0x0
expires=130210000000 softexpires=130210000000
<idle>-0 [000] 130.330711: function:
_raw_spin_unlock_irqrestore
firefox-1722 [001] 130.330711: function:
rt_spin_unlock
firefox-1722 [001] 130.330712: function:
_raw_spin_lock_irqsave
<idle>-0 [000] 130.330712: function:
_raw_spin_lock
firefox-1722 [001] 130.330712: function:
_raw_spin_lock
firefox-1722 [001] 130.330713: function:
_raw_spin_unlock_irqrestore
<idle>-0 [000] 130.330713: sched_switch:
swapper/0:0 [120] R ==> cyclictest:1720 [9]
firefox-1722 [001] 130.330714: function:
_raw_spin_lock_irqsave
cyclictest-1720 [000] 130.330715: function:
_raw_spin_unlock_irq
firefox-1722 [001] 130.330715: function:
_raw_spin_lock
firefox-1722 [001] 130.330716: function:
_raw_spin_unlock_irqrestore
firefox-1722 [001] 130.330718: function:
_raw_spin_lock_irqsave
firefox-1722 [001] 130.330719: function:
_raw_spin_lock
firefox-1722 [001] 130.330719: function:
_raw_spin_unlock_irqrestore
firefox-1722 [001] 130.330722: function:
rt_spin_lock
firefox-1722 [001] 130.330722: function:
_raw_spin_lock_irqsave
firefox-1722 [001] 130.330723: function:
_raw_spin_lock
firefox-1722 [001] 130.330724: function:
_raw_spin_unlock_irqrestore
firefox-1722 [001] 130.330726: function:
rt_spin_lock
firefox-1722 [001] 130.330727: function:
rt_spin_unlock
firefox-1722 [001] 130.330728: function:
rt_spin_lock
firefox-1722 [001] 130.330729: function:
rt_spin_unlock
firefox-1722 [001] 130.330730: function:
rt_spin_unlock
firefox-1722 [001] 130.330731: function:
_raw_spin_lock_irqsave
firefox-1722 [001] 130.330732: function:
_raw_spin_lock
firefox-1722 [001] 130.330733: function:
_raw_spin_unlock_irqrestore
cyclictest-1720 [000] 130.330749: print:
tracing_mark_write: hit latency threshold (84 > 80)
BR
/Song
On Thu, May 7, 2020 at 4:56 PM chen song <lhcs2008@xxxxxxxxx> wrote:
>
> Dear experts,
>
> I had a 4.14.4 kernel with its rtpatch running on a dual-core arm64
> device, the desktop is ubuntu.
>
> In general, the max latency of cyclictest is around 50us in empty load
> which is acceptable. However, if i open a firefox duing cyclictest is
> running, the max latency becomes higher up to 200us.
>
> I tried to use ftrace to debug this issue,"cyclictest -p 90 -m -c 0 -i
> 10 -n -h 100 -q -l 10000000 -b 80", "-b 80" means enable ftrace event
> and terminate cyclictest when latency is higher than 80us.
>
> Here is a piece of log:
>
> 6034916919us+: cpu_idle: state=1 cpu_id=1
> 6034916981us+: hrtimer_cancel: hrtimer=ffffff8012663dc8
> 6034916994us+: sched_waking: comm=cyclictest pid=2321 prio=9 target_cpu=001
> 6034917032us+: cpu_idle: state=4294967295 cpu_id=1
> 6034917044us+: hrtimer_start: hrtimer=ffffffc07ffd5960
> function=tick_sched_timer expires=6034920000000
> softexpires=6034920000000 mode=ABS|PINNED
> 6034917066us+: sys_clock_nanosleep -> 0x0
>
> In this case, I can only see it's stalled in some points but i could'n
> find what happens, in other words, the root cause of the latency.
>
> Is there any better way to debug this issue? I guess some of you might
> meet the same issue, how did you approach to the root cause? I would
> appreciate it so much if you could give me some advice, many thanks.
>
> Best regards,
>
> /Song
>
>
> ============================================================
> Here is the log for reference:
> <idle>-0 1d..h1.. 6034916878us : irq_handler_entry: irq=3
> name=arch_timer -- this is a normal routine
> <idle>-0 1d..h2.. 6034916879us : hrtimer_cancel:
> hrtimer=ffffff8012663dc8
> <idle>-0 1d..h1.. 6034916879us : hrtimer_expire_entry:
> hrtimer=ffffff8012663dc8 function=hrtimer_wakeup now=6034916525493
> <idle>-0 1d..h2.. 6034916880us : sched_waking: comm=cyclictest
> pid=2321 prio=9 target_cpu=001
> <idle>-0 1dn.h3.. 6034916882us : sched_wakeup: comm=cyclictest
> pid=2321 prio=9 target_cpu=001
> <idle>-0 1dn.h1.. 6034916883us : hrtimer_expire_exit:
> hrtimer=ffffff8012663dc8
> <idle>-0 1dn.h1.. 6034916884us : irq_handler_exit: irq=3
> ret=handled
> <idle>-0 1.n..1.. 6034916886us : cpu_idle: state=4294967295
> cpu_id=1
> <idle>-0 1dn..2.. 6034916888us : hrtimer_cancel:
> hrtimer=ffffffc07ffd5960
> <idle>-0 1dn..2.. 6034916890us : hrtimer_start:
> hrtimer=ffffffc07ffd5960 function=tick_sched_timer expires=6034920000000
> softexpires=6034920000000 mode=ABS|PINNED
> <idle>-0 1dn..1.. 6034916891us : rcu_utilization: Start context
> switch
> <idle>-0 1dn..1.. 6034916892us : rcu_utilization: End context
> switch
> <idle>-0 1d...2.. 6034916894us : sched_switch:
> prev_comm=swapper/1 prev_pid=0 prev_prio=120 prev_state=R ==>
> next_comm=cyclictest next_pid=2321 next_prio=9
> cyclicte-2321 1....... 6034916897us : kfree:
> call_site=ffffff80081501f0 ptr= (null)
> cyclicte-2321 1....... 6034916898us : sys_exit: NR 115 = 0
> cyclicte-2321 1....1.. 6034916898us : sys_clock_nanosleep -> 0x0
> cyclicte-2321 1....... 6034916902us : sys_enter: NR 115 (1, 1,
> 7fbd20b448, 0, 0, 7fbd20be00)
> cyclicte-2321 1....1.. 6034916903us :
> sys_clock_nanosleep(which_clock: 1, flags: 1, rqtp: 7fbd20b448, rmtp: 0)
> cyclicte-2321 1....... 6034916904us : hrtimer_init:
> hrtimer=ffffff8012663dc8 clockid=CLOCK_MONOTONIC mode=ABS
> cyclicte-2321 1d...1.. 6034916906us : hrtimer_start:
> hrtimer=ffffff8012663dc8 function=hrtimer_wakeup expires=6034916622448
> softexpires=6034916622448 mode=ABS
> cyclicte-2321 1d...1.. 6034916907us : rcu_utilization: Start context
> switch
> cyclicte-2321 1d...1.. 6034916908us : rcu_utilization: End context switch
> cyclicte-2321 1d...2.. 6034916911us : sched_switch:
> prev_comm=cyclictest prev_pid=2321 prev_prio=9 prev_state=S ==>
> next_comm=swapper/1 next_pid=0 next_prio=120
> <idle>-0 1d...1.. 6034916915us : tick_stop: success=1
> dependency=NONE
> <idle>-0 1d...2.. 6034916916us : hrtimer_cancel:
> hrtimer=ffffffc07ffd5960
> <idle>-0 1d...2.. 6034916917us : hrtimer_start:
> hrtimer=ffffffc07ffd5960 function=tick_sched_timer expires=6035010000000
> softexpires=6035010000000 mode=ABS|PINNED
> <idle>-0 1d...1.. 6034916919us+: cpu_idle: state=1 cpu_id=1
> --(1)
> <idle>-0 1d..h1.. 6034916977us : irq_handler_entry: irq=3
> name=arch_timer
> <idle>-0 1d..h2.. 6034916981us+: hrtimer_cancel:
> hrtimer=ffffff8012663dc8 --(2)
> <idle>-0 1d..h1.. 6034916993us : hrtimer_expire_entry:
> hrtimer=ffffff8012663dc8 function=hrtimer_wakeup now=6034916628193
> <idle>-0 1d..h2.. 6034916994us+: sched_waking: comm=cyclictest
> pid=2321 prio=9 target_cpu=001 --(3)
> <idle>-0 1dn.h3.. 6034917016us : sched_wakeup: comm=cyclictest
> pid=2321 prio=9 target_cpu=001
> <idle>-0 1dn.h1.. 6034917016us : hrtimer_expire_exit:
> hrtimer=ffffff8012663dc8
> <idle>-0 1dn.h1.. 6034917026us : irq_handler_exit: irq=3
> ret=handled
> <idle>-0 1.n..1.. 6034917032us+: cpu_idle: state=4294967295
> cpu_id=1 --(4)
> <idle>-0 1dn..2.. 6034917043us : hrtimer_cancel:
> hrtimer=ffffffc07ffd5960
> <idle>-0 1dn..2.. 6034917044us+: hrtimer_start:
> hrtimer=ffffffc07ffd5960 function=tick_sched_timer expires=6034920000000
> softexpires=6034920000000 mode=ABS|PINNED --(5)
> <idle>-0 1dn..1.. 6034917056us : rcu_utilization: Start context
> switch
> <idle>-0 1dn..1.. 6034917057us : rcu_utilization: End context
> switch
> <idle>-0 1d...2.. 6034917062us : sched_switch:
> prev_comm=swapper/1 prev_pid=0 prev_prio=120 prev_state=R ==>
> next_comm=cyclictest next_pid=2321 next_prio=9
> cyclicte-2321 1....... 6034917065us : kfree:
> call_site=ffffff80081501f0 ptr= (null)
> cyclicte-2321 1....... 6034917066us : sys_exit: NR 115 = 0
> cyclicte-2321 1....1.. 6034917066us+: sys_clock_nanosleep -> 0x0
> --(5)
> cyclicte-2321 1....... 6034917142us : sys_enter: NR 64 (5,
> 7fbd20c500, 1f, 7fbd20bf08, 2, 7fbd20be00)
> cyclicte-2321 1....1.. 6034917143us : sys_write(fd: 5, buf:
> 7fbd20c500, count: 1f)
> cyclicte-2321 1....... 6034917151us : tracing_mark_write: hit latency
> threshold (91 > 80)
> cyclicte-2321 1....... 6034917155us : kfree:
> call_site=ffffff80081501f0 ptr= (null)
> cyclicte-2321 1....... 6034917156us : sys_exit: NR 64 = 31
> cyclicte-2321 1....1.. 6034917157us : sys_write -> 0x1f
> cyclicte-2321 1....... 6034917159us : sys_enter: NR 64 (4, 408650, 1,
> 7fbd20bf08, 2, 7fbd20be00)
> cyclicte-2321 1....1.. 6034917160us : sys_write(fd: 4, buf: 408650,
> count: 1)
