On 12/12/2012 12:41 PM, Preeti U Murthy wrote: > Hi Alex, > On 12/10/2012 01:52 PM, Alex Shi wrote: >> Except using runnable load average in background, move_tasks is also >> the key functions in load balance. We need consider the runnable load >> average in it in order to the apple to apple load comparison. >> >> Signed-off-by: Alex Shi <alex....@intel.com> >> --- >> kernel/sched/fair.c | 11 ++++++++++- >> 1 files changed, 10 insertions(+), 1 deletions(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 6d893a6..bbb069c 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -3741,6 +3741,15 @@ static unsigned long task_h_load(struct task_struct >> *p); >> >> static const unsigned int sched_nr_migrate_break = 32; >> >> +static unsigned long task_h_load_avg(struct task_struct *p) >> +{ >> + u32 period = p->se.avg.runnable_avg_period; >> + if (!period) >> + return 0; >> + >> + return task_h_load(p) * p->se.avg.runnable_avg_sum / period; > ^^^^^^^^^^^^ > This might result in an overflow,considering you are multiplying two 32 > bit integers.Below is how this is handled in > __update_task_entity_contrib in kernel/sched/fair.c > > u32 contrib; > /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */ > contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight); > contrib /= (se->avg.runnable_avg_period + 1); > se->avg.load_avg_contrib = scale_load(contrib);
scale_load_down is do nothing. > > Also why can't p->se.load_avg_contrib be used directly? as a return > value for task_h_load_avg? since this is already updated in > update_task_entity_contrib and update_group_entity_contrib. No, only non task entity goes to update_group_entity_contrib. not task entity. >> +} >> + >> /* >> * move_tasks tries to move up to imbalance weighted load from busiest to >> * this_rq, as part of a balancing operation within domain "sd". >> @@ -3776,7 +3785,7 @@ static int move_tasks(struct lb_env *env) >> if (throttled_lb_pair(task_group(p), env->src_cpu, >> env->dst_cpu)) >> goto next; >> >> - load = task_h_load(p); >> + load = task_h_load_avg(p); >> >> if (sched_feat(LB_MIN) && load < 16 && >> !env->sd->nr_balance_failed) >> goto next; >> > > Regards > Preeti U Murthy > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/