[RFT][patch] Scheduling for HTT and not only

[Alexander Motin]

On 02/15/12 21:54, Jeff Roberson wrote:
> On Wed, 15 Feb 2012, Alexander Motin wrote:
>> I've decided to stop those cache black magic practices and focus on
>> things that really exist in this world -- SMT and CPU load. I've
>> dropped most of cache related things from the patch and made the rest
>> of things more strict and predictable:
>> http://people.freebsd.org/~mav/sched.htt34.patch
>
> This looks great. I think there is value in considering the other
> approach further but I would like to do this part first. It would be
> nice to also add priority as a greater influence in the load balancing
> as well.

I haven't got good idea yet about balancing priorities, but I've 
rewritten balancer itself. As soon as sched_lowest() / sched_highest() 
are more intelligent now, they allowed to remove topology traversing 
from the balancer itself. That should fix double-swapping problem, allow 
to keep some affinity while moving threads and make balancing more fair. 
I did number of tests running 4, 8, 9 and 16 CPU-bound threads on 8 
CPUs. With 4, 8 and 16 threads everything is stationary as it should. 
With 9 threads I see regular and random load move between all 8 CPUs. 
Measurements on 5 minutes run show deviation of only about 5 seconds. It 
is the same deviation as I see caused by only scheduling of 16 threads 
on 8 cores without any balancing needed at all. So I believe this code 
works as it should.

Here is the patch: http://people.freebsd.org/~mav/sched.htt40.patch

I plan this to be a final patch of this series (more to come :)) and if 
there will be no problems or objections, I am going to commit it (except 
some debugging KTRs) in about ten days. So now it's a good time for 
reviews and testing. :)

-- 
Alexander Motin