Re: Regression seen for patch "sched:dont decrease idle sleep avg"

[Peter Williams]

Mike Galbraith wrote:
> On Tue, 2006-05-16 at 16:32 -0700, Tim Chen wrote:
> > On Tue, 2006-05-16 at 09:45 +1000, Con Kolivas wrote:
> >
> > > Yes it's only designed to detect something that has been asleep for an 
> > > arbitrary long time and "categorised as idle"; it is not supposed to be a 
> > > priority stepping stone for everything, in this case at MAX_BONUS-1. Mike 
> > > proposed doing this instead, but it was never my intent. 
> > It seems like just one sleep longer than INTERACTIVE_SLEEP is needed
> > kick the priority of a process all the way to MAX_BONUS-1 and boost the
> > sleep_avg, regardless of what the prior sleep_avg was.
> >
> > So if there is a cpu hog that has long sleeps occasionally, once it woke
> > up, its priority will get boosted close to maximum, likely starving out
> > other processes for a while till its sleep_avg gets reduced.  This
> > behavior seems like something to avoid according to the original code
> > comment.  Are we boosting the priority too quickly?  
>
> The answer to that is, sometimes yes, and when it bites, it bites hard.
> Happily, most hogs don't sleep much, and we don't generally have lots of
> bursty sleepers.

But it's easy for a malicious user to exploit.  Yes?

Peter
--
Peter Williams                                   pwil3058@xxxxxxxxxxxxxx

"Learning, n. The kind of ignorance distinguishing the studious."
 -- Ambrose Bierce
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