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
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