[Bug 100771] When activating ignore_nice_load with governor ondemand performance drops for normal processes.

[Bug 100771] When activating ignore_nice_load with governor ondemand performance drops for normal processes.

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=100771

Aaron Lu <aaron.lu@intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |aaron.lu@intel.com
          Component|Power-Processor             |cpufreq
           Assignee|acpi_power-processor@kernel |cpufreq@vger.kernel.org
                   |-bugs.osdl.org              |
            Product|ACPI                        |Power Management

--- Comment #2 from Aaron Lu <aaron.lu@intel.com> ---
Looks like a cpufreq issue to me, move there.

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[Bug 100771] When activating ignore_nice_load with governor ondemand performance drops for normal processes.

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=100771

--- Comment #3 from Chen Yu <yu.c.chen@intel.com> ---
This is a normal behavior IMO. 

1. task_b with nice = 1 does not mean task_a will always occupy the time slice,
it is CFS scheduler, which means even task with nice = 19 will get chance to
run.
2.When you enable ignore_nice_load, the task_b with nice = 1 will be considered
to be idle, which means that, the total time task_b is running, will be added
to current cpu's idle time, which will cause the cpufreq governor to treat the
cpu load lower than when ignore_nice_load disabled.

Yu

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[Bug 100771] When activating ignore_nice_load with governor ondemand performance drops for normal processes.

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=100771

--- Comment #4 from calvaris@igalia.com ---
(In reply to Chen Yu from comment #3)
> 2.When you enable ignore_nice_load, the task_b with nice = 1 will be
> considered to be idle, which means that, the total time task_b is running,
> will be added to current cpu's idle time, which will cause the cpufreq
> governor to treat the cpu load lower than when ignore_nice_load disabled.

I understand the rationale you explain if we apply it only to idle tasks. What
I don't agree with is that tasks with idle priority can slow down tasks with
normal priority.

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[Bug 100771] When activating ignore_nice_load with governor ondemand performance drops for normal processes.

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=100771

--- Comment #5 from Chen Yu <yu.c.chen@intel.com> ---
(In reply to calvaris from comment #4)
> (In reply to Chen Yu from comment #3)
> > 2.When you enable ignore_nice_load, the task_b with nice = 1 will be
> > considered to be idle, which means that, the total time task_b is running,
> > will be added to current cpu's idle time, which will cause the cpufreq
> > governor to treat the cpu load lower than when ignore_nice_load disabled.
> 
> I understand the rationale you explain if we apply it only to idle tasks.
> What I don't agree with is that tasks with idle priority can slow down tasks
> with normal priority.
Do you mean idle tasks = task_b in above context? Why task_b slows down the
normal priority task is because that, the cpufreq decrease due to task_b's high
nice value, and task_a is scheduled on the same cpu.

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[Bug 100771] When activating ignore_nice_load with governor ondemand performance drops for normal processes.

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https://bugzilla.kernel.org/show_bug.cgi?id=100771

--- Comment #6 from calvaris@igalia.com ---
(In reply to Chen Yu from comment #5)
> Do you mean idle tasks = task_b in above context? Why task_b slows down the
> normal priority task is because that, the cpufreq decrease due to task_b's
> high nice value, and task_a is scheduled on the same cpu.

Yes, I understand that it's what's happenning and I think that is what
shouldn't happen because, IMHO, it doesn't make sense. I think it should be
exactly the opposite, as an idle task is scheduled on the same cpu as a higher
priority one, it should be run at the frequency of the higher one.

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[Bug 100771] When activating ignore_nice_load with governor ondemand performance drops for normal processes.

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=100771

--- Comment #7 from Chen Yu <yu.c.chen@intel.com> ---
(In reply to calvaris from comment #6)
> (In reply to Chen Yu from comment #5)
> > Do you mean idle tasks = task_b in above context? Why task_b slows down the
> > normal priority task is because that, the cpufreq decrease due to task_b's
> > high nice value, and task_a is scheduled on the same cpu.
> 
> Yes, I understand that it's what's happenning and I think that is what
> shouldn't happen because, IMHO, it doesn't make sense. I think it should be
> exactly the opposite, as an idle task is scheduled on the same cpu as a
> higher priority one, it should be run at the frequency of the higher one.

Well, currently the cpufreq framework is based on the total load of one CPU,
but not on single task/or a group of tasks. According to your requirement, it
looks like a 'cgroup' cpufreq scheduling. It would be of another new semantic
IMO.

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[Bug 100771] When activating ignore_nice_load with governor ondemand performance drops for normal processes.

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https://bugzilla.kernel.org/show_bug.cgi?id=100771

Zhang Rui <rui.zhang@intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rui.zhang@intel.com
           Assignee|cpufreq@vger.kernel.org     |yu.c.chen@intel.com

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