On Mon, May 6, 2013 at 2:21 AM, Alex Shi <[email protected]> wrote: > On 05/06/2013 04:19 PM, Paul Turner wrote: >> On Sun, May 5, 2013 at 6:45 PM, Alex Shi <[email protected]> wrote: >>> We need initialize the se.avg.{decay_count, load_avg_contrib} for a >>> new forked task. >>> Otherwise random values of above variables cause mess when do new task >>> enqueue: >>> enqueue_task_fair >>> enqueue_entity >>> enqueue_entity_load_avg >>> >>> and make forking balancing imbalance since incorrect load_avg_contrib. >>> >>> set avg.decay_count = 0, and avg.load_avg_contrib = se->load.weight to >>> resolve such issues. >>> >>> Signed-off-by: Alex Shi <[email protected]> >>> --- >>> kernel/sched/core.c | 6 ++++++ >>> kernel/sched/fair.c | 4 ++++ >>> 2 files changed, 10 insertions(+) >>> >>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >>> index c8db984..ecec7f1 100644 >>> --- a/kernel/sched/core.c >>> +++ b/kernel/sched/core.c >>> @@ -1566,6 +1566,7 @@ static void __sched_fork(struct task_struct *p) >>> #ifdef CONFIG_SMP >>> p->se.avg.runnable_avg_period = 0; >>> p->se.avg.runnable_avg_sum = 0; >>> + p->se.avg.decay_count = 0; >>> #endif >>> #ifdef CONFIG_SCHEDSTATS >>> memset(&p->se.statistics, 0, sizeof(p->se.statistics)); >>> @@ -1653,6 +1654,11 @@ void sched_fork(struct task_struct *p) >>> p->sched_reset_on_fork = 0; >>> } >>> >>> + /* New forked task assumed with full utilization */ >>> +#if defined(CONFIG_SMP) >>> + p->se.avg.load_avg_contrib = p->se.load.weight; >> >> This is missing a scale_load() right? Further: Why not put this in >> __sched_fork? > > scale_load is not working now. Anyway I can add this. > >> >> We should also charge a minimum period to make the numbers a little >> more kosher, e.g.: >> + p->se.avg.runnable_avg_period = 1024; >> + p->se.avg.runnable_avg_sum = 1024; >> >> Rather than exposing the representation of load_avg_contrib to >> __sched_fork it might also be better to call: >> __update_task_entity_contrib(&p->se) >> After the initialization above; this would also avoid potential bugs >> like the missing scale_load() above. > > Above simple change can not work.
Could you provide additional detail here? Note that the sum change I was suggesting above was: __sched_fork(): + p->se.avg.decay_count = 0; + p->se.avg.runnable_avg_period = 1024; + p->se.avg.runnable_avg_sum = 1024; + __update_task_entity_contrib(&p->se); [ Also: move __sched_fork() beyond p->sched_reset_on_fork in sched_fork(). ] > We had talked this solution months ago. And get agreement on this patch. > https://lkml.org/lkml/2013/2/20/48 :) Yes, I made the same suggestion in the last round, see: https://lkml.org/lkml/2013/2/19/176 Your reply there seems like an ack of my suggestion, the only difference I'm seeing is that using __update_task_entity_contrib() as originally suggested is safer since it keeps the representation of load_avg_contrib opaque. > -- > Thanks > Alex -- 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/
