Messages in this thread Patch in this message | | | From | Valentin Schneider <> | Subject | [PATCH 8/8] sched/fair: Relax task_hot() for misfit tasks | Date | Thu, 28 Jan 2021 18:31:41 +0000 |
| |
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.schneider@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)) + return 0; + /* * Buddy candidates are cache hot: */ -- 2.27.0
| |