Re: [patch] CFS scheduler, -v12

[Peter Williams]

Dmitry Adamushko wrote:
> On 18/05/07, Peter Williams <pwil3058@xxxxxxxxxxxxxx> wrote:
> > [...]
> > One thing that might work is to jitter the load balancing interval a
> > bit.  The reason I say this is that one of the characteristics of top
> > and gkrellm is that they run at a more or less constant interval (and,
> > in this case, X would also be following this pattern as it's doing
> > screen updates for top and gkrellm) and this means that it's possible
> > for the load balancing interval to synchronize with their intervals
> > which in turn causes the observed problem.  A jittered load balancing
> > interval should break the synchronization.  This would certainly be
> > simpler than trying to change the move_task() logic for selecting which
> > tasks to move.
>
> Just an(quick) another idea. Say, the load balancer would consider not
> only p->load_weight but also something like Tw(task) =
> (time_spent_on_runqueue / total_task's_runtime) * some_scale_constant
> as an additional "load" component (OTOH, when a task starts, it takes
> some time for this parameter to become meaningful). I guess, it could
> address the scenarios your have described (but maybe break some others
> as well :) ...
> Any hints on why it's stupid?

Well that is the kind of thing I was hoping to avoid for the reasons of 
complexity.  I think that the actual implementation would be more 
complex than it sounds and possibly require multiple runs down the list 
of moveable tasks which would be bad for overhead.

Basically, I don't think that the problem is serious enough to warrant a 
complex solution.  But I may be wrong about how complex the 
implementation would be.

Peter
--
Peter Williams                                   pwil3058@xxxxxxxxxxxxxx

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