Hi,
> On Aug 13, 2020, at 2:39 AM, Dietmar Eggemann <dietmar.eggem...@arm.com>
> wrote:
>
> On 12/08/2020 05:19, benbjiang(蒋彪) wrote:
>> Hi,
>>
>>> On Aug 11, 2020, at 11:54 PM, Dietmar Eggemann <dietmar.eggem...@arm.com>
>>> wrote:
>>>
>>> On 11/08/2020 02:41, benbjiang(蒋彪) wrote:
>>>> Hi,
>>>>
>>>>> On Aug 10, 2020, at 9:24 PM, Dietmar Eggemann <dietmar.eggem...@arm.com>
>>>>> wrote:
>>>>>
>>>>> On 06/08/2020 17:52, benbjiang(蒋彪) wrote:
>>>>>> Hi,
>>>>>>
>>>>>>> On Aug 6, 2020, at 9:29 PM, Dietmar Eggemann <dietmar.eggem...@arm.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>> On 03/08/2020 13:26, benbjiang(蒋彪) wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>> On Aug 3, 2020, at 4:16 PM, Dietmar Eggemann
>>>>>>>>> <dietmar.eggem...@arm.com> wrote:
>>>>>>>>>
>>>>>>>>> On 01/08/2020 04:32, Jiang Biao wrote:
>>>>>>>>>> From: Jiang Biao <benbji...@tencent.com>
>
> [...]
>
>>> Trace a run of 2 SCHED_OTHER (nice 0) tasks and 1 SCHED_IDLE task on a
>>> single CPU and trace_printk the conditions 'if (delta < 0)' and ' if
>>> (delta > ideal_runtime)' in check_preempt_tick().
>>>
>>> Then do the same with 3 SCHED_OTHER (nice 0) tasks. You can also change
>>> the niceness of the 2 SCHED_OTHER task to 19 to see some differences in
>>> the kernelshark's task layout.
>>>
>>> rt-app (https://github.com/scheduler-tools/rt-app) is a nice tool to
>>> craft those artificial use cases.
>> With rt-app tool, sched_switch traced by ftrace, the result is as what I
>> expected,
>
> I use:
>
> {
> "tasks" : {
> "task_other" : {
> "instance" : 2,
> "loop" : 200,
> "policy" : "SCHED_OTHER",
> "run" : 8000,
> "timer" : { "ref" : "unique1" , "period" : 16000,
> "mode" : "absolute" },
> "priority" : 0
> },
> "task_idle" : {
> "instance" : 1,
> "loop" : 200,
> "policy" : "SCHED_IDLE",
> "run" : 8000,
> "timer" : { "ref" : "unique2" , "period" : 16000,
> "mode" : "absolute" }
> }
> },
> "global" : {
> "calibration" : 243, <-- Has to be calibrated against the CPU
> you run on !!!
> "default_policy" : "SCHED_OTHER",
> "duration" : -1
> }
> }
>
> to have 2 (periodic) SCHED_OTHER and 1 SCHED_IDLE task.
>
>> ** 2normal+1idle: idle preempt normal every 600+ms **
>
> During the 3.2s the 2 SCHED_OTHER tasks run, the SCHED_IDLE task is
> switched in only once, after ~2.5s.
Use your config with loop increased from 200 to 2000, to observe longer,
<...>-37620 [002] d... 47950.446191: sched_switch:
prev_comm=task_other-1 prev_pid=37620 prev_prio=120 prev_state=S ==>
next_comm=task_idle-2 next_pid=37621 next_prio=120
<...>-37619 [002] d... 47955.687709: sched_switch:
prev_comm=task_other-0 prev_pid=37619 prev_prio=120 prev_state=R ==>
next_comm=task_idle-2 next_pid=37621 next_prio=120
// The first preemption interval is 5.2s.
<...>-37620 [002] d... 47956.375716: sched_switch:
prev_comm=task_other-1 prev_pid=37620 prev_prio=120 prev_state=R ==>
next_comm=task_idle-2 next_pid=37621 next_prio=120
<...>-37619 [002] d... 47957.060722: sched_switch:
prev_comm=task_other-0 prev_pid=37619 prev_prio=120 prev_state=R ==>
next_comm=task_idle-2 next_pid=37621 next_prio=120
<...>-37620 [002] d... 47957.747728: sched_switch:
prev_comm=task_other-1 prev_pid=37620 prev_prio=120 prev_state=R ==>
next_comm=task_idle-2 next_pid=37621 next_prio=120
<...>-37620 [002] d... 47958.423734: sched_switch:
prev_comm=task_other-1 prev_pid=37620 prev_prio=120 prev_state=R ==>
next_comm=task_idle-2 next_pid=37621 next_prio=120
<...>-37620 [002] d... 47959.119740: sched_switch:
prev_comm=task_other-1 prev_pid=37620 prev_prio=120 prev_state=R ==>
next_comm=task_idle-2 next_pid=37621 next_prio=120
// After the first preemption, the rest preemption intervals are all about
600ms+. :)
>
>> ** 3normal+idle: idle preempt normal every 1000+ms **
>
> Ah, this was meant to be 3 SCHED_OTHER tasks only! To see the difference
> in behavior.
With 3 SCHED_OHTER tasks only, the SCHED_OHTER task is switched in
Every 27ms.
>
>> ** 2normal(nice 19)+1idle(nice 0): idle preempt normal every 30+ms **
>
> During the 3.2s the 2 SCHED_OTHER tasks run, the SCHED_IDLE task is
> switched in every ~45ms.
That’s as what I expected. :)
Thx.
Regards,
Jiang
>
> [...]
