On Thu, Jun 20, 2013 at 10:45:38PM +0200, Frederic Weisbecker wrote: > If we run in full dynticks mode, we currently have no way to > correctly update the secondary decaying indexes of the CPU > load stats as it is typically maintained by update_cpu_load_active() > at each tick. > > We have an available infrastructure that handles tickless loads > (cf: decay_load_missed) but it seems to only work for idle tickless > loads, which only applies if the CPU hasn't run any real task but > idle on the tickless timeslice. > > Until we can provide a sane mathematical solution to handle full > dynticks loads, lets simply deactivate the LB_BIAS sched feature > if CONFIG_NO_HZ_FULL as it is currently the only user of the decayed > load records. > > The first load index that represents the current runqueue load weight > is still maintained and usable. > > Signed-off-by: Frederic Weisbecker <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Li Zhong <[email protected]> > Cc: Paul E. McKenney <[email protected]>
Acked-by: Paul E. McKenney <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Steven Rostedt <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Borislav Petkov <[email protected]> > Cc: Alex Shi <[email protected]> > Cc: Paul Turner <[email protected]> > Cc: Mike Galbraith <[email protected]> > Cc: Vincent Guittot <[email protected]> > --- > kernel/sched/fair.c | 13 +++++++++++-- > kernel/sched/features.h | 3 +++ > 2 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index c0ac2c3..2e8df6f 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -2937,6 +2937,15 @@ static unsigned long weighted_cpuload(const int cpu) > return cpu_rq(cpu)->load.weight; > } > > +static inline int sched_lb_bias(void) > +{ > +#ifndef CONFIG_NO_HZ_FULL > + return sched_feat(LB_BIAS); > +#else > + return 0; > +#endif > +} > + > /* > * Return a low guess at the load of a migration-source cpu weighted > * according to the scheduling class and "nice" value. > @@ -2949,7 +2958,7 @@ static unsigned long source_load(int cpu, int type) > struct rq *rq = cpu_rq(cpu); > unsigned long total = weighted_cpuload(cpu); > > - if (type == 0 || !sched_feat(LB_BIAS)) > + if (type == 0 || !sched_lb_bias()) > return total; > > return min(rq->cpu_load[type-1], total); > @@ -2964,7 +2973,7 @@ static unsigned long target_load(int cpu, int type) > struct rq *rq = cpu_rq(cpu); > unsigned long total = weighted_cpuload(cpu); > > - if (type == 0 || !sched_feat(LB_BIAS)) > + if (type == 0 || !sched_lb_bias()) > return total; > > return max(rq->cpu_load[type-1], total); > diff --git a/kernel/sched/features.h b/kernel/sched/features.h > index 99399f8..635f902 100644 > --- a/kernel/sched/features.h > +++ b/kernel/sched/features.h > @@ -43,7 +43,10 @@ SCHED_FEAT(ARCH_POWER, true) > > SCHED_FEAT(HRTICK, false) > SCHED_FEAT(DOUBLE_TICK, false) > + > +#ifndef CONFIG_NO_HZ_FULL > SCHED_FEAT(LB_BIAS, true) > +#endif > > /* > * Decrement CPU power based on time not spent running tasks > -- > 1.7.5.4 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
