2016-04-21 6:28 GMT+08:00 Rafael J. Wysocki <rafael.j.wyso...@intel.com>:
> On 4/21/2016 12:24 AM, Wanpeng Li wrote:
>>
>> 2016-04-20 22:01 GMT+08:00 Peter Zijlstra <pet...@infradead.org>:
>>>
>>> On Wed, Apr 20, 2016 at 02:32:35AM +0200, Rafael J. Wysocki wrote:
>>>>
>>>> On Monday, April 18, 2016 01:51:24 PM Wanpeng Li wrote:
>>>>>
>>>>> Sometimes update_curr() is called w/o tasks actually running, it is
>>>>> captured by:
>>>>> u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start;
>>>>> We should not trigger cpufreq update in this case for rt/deadline
>>>>> classes, and this patch fix it.
>>>>>
>>>>> Signed-off-by: Wanpeng Li <wanpeng...@hotmail.com>
>>>>
>>>> The signed-off-by tag should agree with the From: header. One way to
>>>> achieve
>>>> that is to add an extra From: line at the start of the changelog.
>>>>
>>>> That said, this looks like a good catch that should go into 4.6 to me.
>>>>
>>>> Peter, what do you think?
>>>
>>> I'm confused by the Changelog. *what* ?
>>
>> Sometimes .update_curr hook is called w/o tasks actually running, it is
>> captured by:
>>
>> u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start;
>>
>> We should not trigger cpufreq update in this case for rt/deadline
>> classes, and this patch fix it.
>
>
> That's what you wrote in the changelog, no need to repeat that.
>
> I guess Peter is asking for more details, though. I actually would like to
> get some more details here too. Like an example of when the situation in
> question actually happens.
I add a print to print when delta_exec is zero for rt class, something
like below:
watchdog/5-48 [005] d... 568.449095: update_curr_rt: rt
delta_exec is zero
watchdog/5-48 [005] d... 568.449104: <stack trace>
=> pick_next_task_rt
=> __schedule
=> schedule
=> smpboot_thread_fn
=> kthread
=> ret_from_fork
watchdog/5-48 [005] d... 568.449105: update_curr_rt: rt
delta_exec is zero
watchdog/5-48 [005] d... 568.449111: <stack trace>
=> put_prev_task_rt
=> pick_next_task_idle
=> __schedule
=> schedule
=> smpboot_thread_fn
=> kthread
=> ret_from_fork
watchdog/6-56 [006] d... 568.510094: update_curr_rt: rt
delta_exec is zero
watchdog/6-56 [006] d... 568.510103: <stack trace>
=> pick_next_task_rt
=> __schedule
=> schedule
=> smpboot_thread_fn
=> kthread
=> ret_from_fork
watchdog/6-56 [006] d... 568.510105: update_curr_rt: rt
delta_exec is zero
watchdog/6-56 [006] d... 568.510111: <stack trace>
=> put_prev_task_rt
=> pick_next_task_idle
=> __schedule
=> schedule
=> smpboot_thread_fn
=> kthread
=> ret_from_fork
[...]
Regards,
Wanpeng Li
