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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