Re: Nick's scheduler v17

[Andrew Theurer <habanero@us.ibm.com>]

On Friday 24 October 2003 13:10, Nick Piggin wrote:
> Hi,
> http://www.kerneltrap.org/~npiggin/v17/
>
> Still working on SMP and NUMA. Some (maybe) interesting things I put in are
> - Sequential CPU balancing so you don't get a big storm of balances
> every 1/4s.
> - Balancing is trying to err more on the side of caution, I have to start
>   analysing it more thoroughly though.

+
+	*imbalance /= 2;
+	*imbalance = (*imbalance + FPT - 1) / FPT;

I think I see what is going on here, but would something like this work out 
better?

	*imbalance = min(this_load - load_avg, load_avg - max_load)

That way you take just enough to either have busiest_queue or this_rq's length 
be the load_avg.  I suppose you could take even less, but IMO, the /=2 is 
what I really don't like.  Perhaps:

*imbalance = min(this_load - load_avg, load_avg - max_load);
*imbalance = (*imbalance + FPT - 1) / FPT;

This should work well for intranode balances, internode balances may need a 
little optimization, since the load_avg really does not really represent the 
load avg of the two nodes in question, just one cpu from one of them and all 
the cpus from another.