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SubjectRe: [PATCH] sched: Fix adverse effects of NFS client on interactive response
At 10:31 PM 1/5/2006 +1100, Peter Williams wrote:
>Mike Galbraith wrote:
>>At 08:51 AM 1/5/2006 +1100, Peter Williams wrote:
>>
>>>I think that some of the harder to understand parts of the scheduler
>>>code are actually attempts to overcome the undesirable effects (such as
>>>those I've described) of inappropriately identifying tasks as
>>>interactive. I think that it would have been better to attempt to fix
>>>the inappropriate identifications rather than their effects and I think
>>>the prudent use of TASK_NONINTERACTIVE is an important tool for achieving this.
>>
>>IMHO, that's nothing but a cover for the weaknesses induced by using
>>exclusively sleep time as an information source for the priority
>>calculation. While this heuristic does work pretty darn well, it's
>>easily fooled (intentionally or otherwise). The challenge is to find the
>>right low cost informational component, and to stir it in at O(1).
>
>TASK_NONINTERACTIVE helps in this regard, is no cost in the code where
>it's used and probably decreases the costs in the scheduler code by
>enabling some processing to be skipped. If by its judicious use the
>heuristic is only fed interactive sleep data the heuristics accuracy in
>identifying interactive tasks should be improved. It may also allow the
>heuristic to be simplified.

I disagree. You can nip and tuck all the bits of sleep time you want, and
it'll just shift the lumpy spots around (btdt).

-Mike

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