Re: [rfc patch] sched/fair: Use instantaneous load for fork/exec balancing

[Yuyang Du]

On Tue, Jun 14, 2016 at 09:58:31AM +0200, Mike Galbraith wrote:
> SUSE's regression testing noticed that...
> 
> 0905f04eb21f sched/fair: Fix new task's load avg removed from source CPU in wake_up_new_task()
> 
> ...introduced a hackbench regression, and indeed it does.  I think this
> regression has more to do with randomness than anything else, but in
> general...
> 
> While averaging calms down load balancing, helping to keep migrations
> down to a dull roar, it's not completely wonderful when it comes to
> things that live in the here and now, hackbench being one such.
> 
> time sh -c 'for i in `seq 1000`; do hackbench -p -P > /dev/null; done'
> 
> real    0m55.397s
> user    0m8.320s
> sys     5m40.789s
> 
> echo LB_INSTANTANEOUS_LOAD > /sys/kernel/debug/sched_features
> 
> real    0m48.049s
> user    0m6.510s
> sys     5m6.291s
> 
> Signed-off-by: Mike Galbraith <umgwanakikbuti@xxxxxxxxx>

I am entirely for giving it a "clear unadulterated reality", and even
more for it an option.

Reviewed-by: Yuyang Du <yuyang.du@xxxxxxxxx>