Re: smpnice: issues with finding busiest queue

[Peter Williams <pwil3058@bigpond.net.au>]

Siddha, Suresh B wrote:
> On Thu, Apr 13, 2006 at 10:05:51AM +1000, Peter Williams wrote:
>> There be dragons here :-(.
>>
> 
> At more places in this part of the world (smpnice) :)
> 
> We need to relook at find_busiest_queue()... With the current weighted
> calculations, it doesn't always make sense to look at the highest weighted
> runqueue in the busy group..
> 
> for example on a DP with HT system, how does the load balance behave with
> Package-0 containing one high priority and one low priority, Package-1
> containing one low priority(with other thread being idle)..
> 
> Package-1 thinks that it need to take the low priority thread from Package-0.
> And find_busiest_queue() returns the cpu thread with highest priority task..
> And ultimately(with help of active load balance) we move high priority
> task to Package-1. And same continues with Package-0 now, moving high priority
> task from package-1 to package-0..
> 
> Even without the presence of active load balance, load balance will fail
> to balance(having two low priority tasks on one package, and high
> priority task on another package) the above scenario....
> 
> We probably need to use imbalance(and more factors) to determine the busiest 
> queue in the group.....

A patch would be nice.

-- 
Peter Williams                                   pwil3058@bigpond.net.au

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