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
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