On Thu, May 29, 2014 at 09:37:39PM +0200, Vincent Guittot wrote:
On 29 May 2014 11:50, Peter Zijlstra peterz@infradead.org wrote:
On Fri, May 23, 2014 at 05:53:04PM +0200, Vincent Guittot wrote:
If the CPU is used for handling lot of IRQs, trig a load balance to check if it's worth moving its tasks on another CPU that has more capacity
Signed-off-by: Vincent Guittot vincent.guittot@linaro.org
kernel/sched/fair.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e8a30f9..2501e49 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5948,6 +5948,13 @@ static bool update_sd_pick_busiest(struct lb_env *env, if (sgs->sum_nr_running > sgs->group_capacity) return true;
/** The group capacity is reduced probably because of activity from other* sched class or interrupts which use part of the available capacity*/if ((sg->sgp->power_orig * 100) > (sgs->group_power * env->sd->imbalance_pct))return true;if (sgs->group_imb) return true;But we should already do this because the load numbers are scaled with the power/capacity figures. If one CPU gets significant less time to run fair tasks, its effective load would spike and it'd get to be selected here anyway.
Or am I missing something?
The CPU could have been picked when the capacity becomes null (which occurred when the cpu_power goes below half the default SCHED_POWER_SCALE). And even after that, there were some conditions in find_busiest_group that was bypassing this busiest group
Could you detail those conditions? FWIW those make excellent Changelog material.