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.guittot@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