Re: [PATCH] remove interactive credit

[Bill Davidsen]

Nick Piggin wrote:
> Con Kolivas wrote:
>
> > remove interactive credit
> >
> >
> >
> > ------------------------------------------------------------------------
> >
> > Special casing tasks by interactive credit was helpful for preventing 
> > fully
> > cpu bound tasks from easily rising to interactive status.
> > However it did not select out tasks that had periods of being fully 
> > cpu bound
> > and then sleeping while waiting on pipes, signals etc. This led to a more
> > disproportionate share of cpu time.
> >
> > Backing this out will no longer special case only fully cpu bound 
> > tasks, and
> > prevents the variable behaviour that occurs at startup before tasks 
> > declare
> > themseleves interactive or not, and speeds up application startup 
> > slightly
> > under certain circumstances. It does cost in interactivity slightly as 
> > load
> > rises but it is worth it for the fairness gains.
> >
> > Signed-off-by: Con Kolivas <kernel@xxxxxxxxxxx>
>
> I'm scared :(
>
> I'm in favour of any attempts to simplify things... but will it be two
> months or three before this spontaneously explodes for half our userbase?
>
> Andrew's boss so he gets to decide >:)

If I read the intent right, this is an example of worst case avoidance, 
where a little average interactivity is traded for preventing the case 
where a single misguided process gets most/all of the CPU and 
performance falls off the edge of the table. As a user I see that as the 
same line of thought which gave us low-latency patches, to trade a 
miniscule bit of one thing to avoid something really undesirable.

I suspect there will be people who don't want to make this trade, 
although it sounds like a good one to me.

--
   -bill davidsen (davidsen@xxxxxxx)
"The secret to procrastination is to put things off until the
 last possible moment - but no longer"  -me
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