linux-kernel - Re: [RFC][PATCH] sched: fix GENTLE_FAIR

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Message-ID: <4B190ACA.6090901@suse.de>
Date:	Fri, 04 Dec 2009 18:42:42 +0530
From:	Suresh Jayaraman <sjayaraman@...e.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] sched: fix GENTLE_FAIR_SLEEPERS dependency

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
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