Re: [RFC][PATCH] sched: fix GENTLE_FAIR_SLEEPERS dependency

Suresh Jayaraman
2009-12-04T13:12:43Z

On 12/04/2009 05:38 PM, Peter Zijlstra wrote:
> On Fri, 2009-12-04 at 17:12 +0530, Suresh Jayaraman wrote:
>> On 12/04/2009 04:38 PM, Peter Zijlstra wrote:
>>> On Fri, 2009-12-04 at 15:50 +0530, Suresh Jayaraman wrote:
>>>>
>>>> I think originally introduced as a development/debugging facility,
>>>> sched_features is slowly transforming into a viable tool for System
>>>> Administrators, by looking at the impact of turning on/off some of these
>>>> features on some workloads (especially non-desktop workloads). And I
>>>> think these benefits should be passed on to the end users perhaps in the
>>>> form of documentation.
>>>
>>> This is really not meant to be used in that context. Its purely a debug
>>> feature, with knobs coming and going as we see fit.
>>>
>>
>> Does this also mean these features should not impact any specific
>> workload much?
>
> How would that follow?
>
>> http://osdir.com/ml/linux-kernel/2009-09/msg03406.html
>> In the thread above Ingo mentions about a few features and my
>> understanding is that some of these might favour one type of workload
>> than other. Is this not true anymore?
>
> Sure it is, everything is workload dependent, the posix SCHED_OTHER task
> model just doesn't include much usable information.
>
> But that does not justify promoting this to generic tunable. What if you
> happen to want to run two different workloads on one machine?

Ok, I understand.

>
> Furthermore, if your favourite workload doesn't work well, file a bug
> report (preferably with reproducer, otherwise its pure guesswork).

Make sense.

> The only reason to poke at it is debugging, full stop, no whining or .33
> won't have the interface anymore, which would be sad because then
> everybody will have to recompile their kernel to debug things.
>

The intention was to understand better (if at all there is anything
tunable, if yes document) and definitely not whining. Please don't kill it.

Thanks,

--
Suresh Jayaraman