Re: [PATCH v3 4/5] sched/pelt: Add a new runnable average signal

[Mel Gorman <mgorman@techsingularity.net>]

On Wed, Feb 19, 2020 at 01:55:13PM +0100, Vincent Guittot wrote:
> Now that runnable_load_avg has been removed, we can replace it by a new
> signal that will highlight the runnable pressure on a cfs_rq. This signal
> track the waiting time of tasks on rq and can help to better define the
> state of rqs.
> 
> At now, only util_avg is used to define the state of a rq:
>   A rq with more that around 80% of utilization and more than 1 tasks is
>   considered as overloaded.
> 
> But the util_avg signal of a rq can become temporaly low after that a task
> migrated onto another rq which can bias the classification of the rq.
> 
> When tasks compete for the same rq, their runnable average signal will be
> higher than util_avg as it will include the waiting time and we can use
> this signal to better classify cfs_rqs.
> 
> The new runnable_avg will track the runnable time of a task which simply
> adds the waiting time to the running time. The runnable _avg of cfs_rq
> will be the /Sum of se's runnable_avg and the runnable_avg of group entity
> will follow the one of the rq similarly to util_avg.
> 
> Tested-by: Valentin Schneider <valentin.schneider@arm.com>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>

Thanks.

Picked up and included in "Reconcile NUMA balancing decisions with the
load balancer v4". The only change I made to your patches was move the
reintroduction of cpu_runnable to the patch that requires it to avoid a
build warning.

-- 
Mel Gorman
SUSE Labs