Re: [Syllable-kernel] Possible scheduler patch

[Daniel G. <da...@fp...>]

On Tue, 2005-01-11 at 21:32 +0000, Kristian Van Der Vliet wrote:
> 
> One change I've considered is rather than trying to calculate the CPU time 
> over the total life of the thread is to keep a count of the number of times a 
> thread runs to the end of it's quantum.  If the quantum expires the counter 
> increments by one.  If the thread blocks before the quantum expires the 
> counter is decremented by one.  The penalty would then be applied according 
> to the counter value.  Threads with a count of five would be scaled back by 
> -10, a count of ten by -20, fifteen by -30 etc. (The real numbers would 
> probably require some tuning)  The advantage here is that the calculation is 
> much easier.  It also solves the problem where threads which have spent a 
> long time idle suddenly shoot to 100% CPU usage.  Under the current 
> calculation based on the total life of the thread the CPU usage would still 
> be calculated as a low percentage and no penalty imposed.  Under the new 
> scheme a thread at 100% CPU would quickly acumulate a high count, and be 
> penalized.

Yes, that sounds generally better.  Another possibility is a decaying
average, which ends up being very similar to what you want to do.

In general, the current method you used will help in the normal case of
a run-away thread.  It's much more unlikely, in my opinion, for a thread
to sleep for a long time and then go berzerk. :)

Still, it'll likely be an improvement.  I'll try and get the kernel
built on my box here and get some ideas and testing in.

> 
> I'll apply your patches tommorow and I'll try out my counter scheme and let 
> you all know how that works out, too.
> 

Thanks.

Daniel