On Thu, 28 Jan 2021 at 19:32, Valentin Schneider <valentin.schnei...@arm.com> wrote: > > Misfit tasks can and will be preempted by the stopper to migrate them over > to a higher-capacity CPU. However, when runnable but not current misfit > tasks are scanned by the load balancer (i.e. detach_tasks()), the > task_hot() ratelimiting logic may prevent us from enqueuing said task onto > a higher-capacity CPU. > > Align detach_tasks() with the active-balance logic and let it pick a > cache-hot misfit task when the destination CPU can provide a capacity > uplift. > > Signed-off-by: Valentin Schneider <valentin.schnei...@arm.com> > --- > kernel/sched/fair.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index cba9f97d9beb..c2351b87824f 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -7484,6 +7484,17 @@ static int task_hot(struct task_struct *p, struct > lb_env *env) > if (env->sd->flags & SD_SHARE_CPUCAPACITY) > return 0; > > + /* > + * On a (sane) asymmetric CPU capacity system, the increase in compute > + * capacity should offset any potential performance hit caused by a > + * migration. > + */ > + if (sd_has_asym_cpucapacity(env->sd) && > + env->idle != CPU_NOT_IDLE && > + !task_fits_capacity(p, capacity_of(env->src_cpu)) && > + cpu_capacity_greater(env->dst_cpu, env->src_cpu))
Why not using env->migration_type to directly detect that it's a misfit task active migration ? > + return 0; > + > /* > * Buddy candidates are cache hot: > */ > -- > 2.27.0 >
