* NO_HZ and ktimersoftd
@ 2017-01-05 9:29 Federico Reghenzani
2017-01-05 16:32 ` Julia Cartwright
0 siblings, 1 reply; 4+ messages in thread
From: Federico Reghenzani @ 2017-01-05 9:29 UTC (permalink / raw)
To: linux-rt-users
Hi all,
I'm trying to setup a RT Linux system (currently on 4.8.2 PREEMPT_RT
patched), and I enabled he NO_HZ_FULL flag in order to reduce the
scheduling interrupts jitter. Trying to isolate one core, I also moved
all interrupts and threads to other CPUs.
This works fine, however when I run my RT application, the thread
kimersoftd is always in "running" state, thus the scheduling interrupt
triggers (because there exists more than 1 task available to run).
Consequently, the advantages of NO_HZ_FULL are vanished.
With kernel trace I found these events on the isolated CPU:
user_loop-772 [003] d..h... 419.818172: softirq_raise:
vec=1 [action=TIMER]
user_loop-772 [003] d...2.. 419.818174: sched_switch:
prev_comm=user_loop prev_pid=772 prev_prio=120 prev_state=R ==>
next_comm=ktimersoftd/3 next_pid=41 next_prio=98
ktimersoftd/3-41 [003] .....11 419.818175: softirq_entry:
vec=1 [action=TIMER]
ktimersoftd/3-41 [003] .....11 419.818176: softirq_exit: vec=1
[action=TIMER]
ktimersoftd/3-41 [003] d...2.. 419.818177: sched_switch:
prev_comm=ktimersoftd/3 prev_pid=41 prev_prio=98 prev_state=S ==>
next_comm=user_loop next_pid=772 next_prio=120
I don't know why ktimersoftd is running at every tick.
Thank you in advance for any hint,
Federico
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: NO_HZ and ktimersoftd
2017-01-05 9:29 NO_HZ and ktimersoftd Federico Reghenzani
@ 2017-01-05 16:32 ` Julia Cartwright
2017-02-23 18:01 ` Sebastian Andrzej Siewior
0 siblings, 1 reply; 4+ messages in thread
From: Julia Cartwright @ 2017-01-05 16:32 UTC (permalink / raw)
To: Federico Reghenzani; +Cc: linux-rt-users
On Thu, Jan 05, 2017 at 10:29:57AM +0100, Federico Reghenzani wrote:
> Hi all,
>
Hello-
> I'm trying to setup a RT Linux system (currently on 4.8.2 PREEMPT_RT
> patched), and I enabled he NO_HZ_FULL flag in order to reduce the
> scheduling interrupts jitter. Trying to isolate one core, I also moved
> all interrupts and threads to other CPUs.
>
> This works fine, however when I run my RT application, the thread
> kimersoftd is always in "running" state, thus the scheduling interrupt
> triggers (because there exists more than 1 task available to run).
> Consequently, the advantages of NO_HZ_FULL are vanished.
This sounds like the same problem that Haris (cc'd) has looked into and
has put together a proposed solution. See the thread here:
http://www.spinics.net/lists/linux-rt-users/msg16113.html
Julia
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: NO_HZ and ktimersoftd
2017-01-05 16:32 ` Julia Cartwright
@ 2017-02-23 18:01 ` Sebastian Andrzej Siewior
2017-03-01 9:23 ` Federico Reghenzani
0 siblings, 1 reply; 4+ messages in thread
From: Sebastian Andrzej Siewior @ 2017-02-23 18:01 UTC (permalink / raw)
To: Federico Reghenzani; +Cc: Julia Cartwright, linux-rt-users
On 2017-01-05 10:32:10 [-0600], Julia Cartwright wrote:
> > This works fine, however when I run my RT application, the thread
> > kimersoftd is always in "running" state, thus the scheduling interrupt
> > triggers (because there exists more than 1 task available to run).
> > Consequently, the advantages of NO_HZ_FULL are vanished.
>
> This sounds like the same problem that Haris (cc'd) has looked into and
> has put together a proposed solution. See the thread here:
>
> http://www.spinics.net/lists/linux-rt-users/msg16113.html
can you please check latest v4.9.11-rt9 if the issue is still there or
gone?
Sebastian
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: NO_HZ and ktimersoftd
2017-02-23 18:01 ` Sebastian Andrzej Siewior
@ 2017-03-01 9:23 ` Federico Reghenzani
0 siblings, 0 replies; 4+ messages in thread
From: Federico Reghenzani @ 2017-03-01 9:23 UTC (permalink / raw)
To: Sebastian Andrzej Siewior
Cc: Federico Reghenzani, Julia Cartwright, linux-rt-users
2017-02-23 19:01 GMT+01:00 Sebastian Andrzej Siewior <bigeasy@linutronix.de>:
> On 2017-01-05 10:32:10 [-0600], Julia Cartwright wrote:
>> > This works fine, however when I run my RT application, the thread
>> > kimersoftd is always in "running" state, thus the scheduling interrupt
>> > triggers (because there exists more than 1 task available to run).
>> > Consequently, the advantages of NO_HZ_FULL are vanished.
>>
>> This sounds like the same problem that Haris (cc'd) has looked into and
>> has put together a proposed solution. See the thread here:
>>
>> http://www.spinics.net/lists/linux-rt-users/msg16113.html
>
> can you please check latest v4.9.11-rt9 if the issue is still there or
> gone?
>
> Sebastian
It seems fixed, thank you
Cheers,
Federico
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-03-01 10:59 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-01-05 9:29 NO_HZ and ktimersoftd Federico Reghenzani
2017-01-05 16:32 ` Julia Cartwright
2017-02-23 18:01 ` Sebastian Andrzej Siewior
2017-03-01 9:23 ` Federico Reghenzani
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