Hi Vincent,
On 08/26/2014 04:36 PM, Vincent Guittot wrote:
> The computation of avg_load and avg_load_per_task should only takes into
> account the number of cfs tasks. The non cfs task are already taken into
> account by decreasing the cpu's capacity and they will be tracked in the
> CPU's utilization (group_utilization) of the next patches
>
> Signed-off-by: Vincent Guittot <vincent.guit...@linaro.org>
> ---
> kernel/sched/fair.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 87b9dc7..b85e9f7 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4092,7 +4092,7 @@ static unsigned long capacity_of(int cpu)
> static unsigned long cpu_avg_load_per_task(int cpu)
> {
> struct rq *rq = cpu_rq(cpu);
> - unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
> + unsigned long nr_running = ACCESS_ONCE(rq->cfs.h_nr_running);
> unsigned long load_avg = rq->cfs.runnable_load_avg;
>
> if (nr_running)
> @@ -5985,7 +5985,7 @@ static inline void update_sg_lb_stats(struct lb_env
> *env,
> load = source_load(i, load_idx);
>
> sgs->group_load += load;
> - sgs->sum_nr_running += rq->nr_running;
> + sgs->sum_nr_running += rq->cfs.h_nr_running;
>
> if (rq->nr_running > 1)
> *overload = true;
>
Why do we probe rq->nr_running while we do load balancing? Should not we
be probing cfs_rq->nr_running instead? We are interested after all in
load balancing fair tasks right? The reason I ask this is, I was
wondering if we need to make the above similar change in more places in
load balancing.
To cite examples: The above check says a cpu is overloaded when
rq->nr_running > 1. However if these tasks happen to be rt tasks, we
would anyway not be able to load balance. So while I was looking through
this patch, I noticed this and wanted to cross verify if we are checking
rq->nr_running on purpose in some places in load balancing; another
example being in nohz_kick_needed().
Regards
Preeti U Murthy
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