Messages in this thread Patch in this message |  | | From | Qais Yousef <> | Subject | [PATCH v3 6/6] sched/rt: Fix pushing unfit tasks to a better CPU | Date | Mon, 2 Mar 2020 13:27:21 +0000 |
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If a task was running on unfit CPU we could ignore migrating if the priority level of the new fitting CPU is the *same* as the unfit one.
Add an extra check to select_task_rq_rt() to allow the push in case:
* p->prio == new_cpu.highest_priority * task_fits(p, new_cpu)
Fixes: 804d402fb6f6 ("sched/rt: Make RT capacity-aware") Signed-off-by: Qais Yousef <qais.yousef@arm.com> --- kernel/sched/rt.c | 41 ++++++++++++++++++++++++++++------------- 1 file changed, 28 insertions(+), 13 deletions(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index ce230bec6847..8aaa442e4867 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1474,20 +1474,35 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags) if (test || !rt_task_fits_capacity(p, cpu)) { int target = find_lowest_rq(p); - /* - * Bail out if we were forcing a migration to find a better - * fitting CPU but our search failed. - */ - if (!test && target != -1 && !rt_task_fits_capacity(p, target)) - goto out_unlock; + if (target != -1) { + bool fit_target = rt_task_fits_capacity(p, target); - /* - * Don't bother moving it if the destination CPU is - * not running a lower priority task. - */ - if (target != -1 && - p->prio < cpu_rq(target)->rt.highest_prio.curr) - cpu = target; + /* + * Bail out if we were forcing a migration to find a + * better fitting CPU but our search failed. + */ + if (!test && !fit_target) + goto out_unlock; + + /* + * Don't bother moving it if the destination CPU is + * not running a lower priority task. + */ + if (p->prio < cpu_rq(target)->rt.highest_prio.curr) { + + cpu = target; + + } else if (p->prio == cpu_rq(target)->rt.highest_prio.curr) { + + /* + * If the priority is the same and the new CPU + * is a better fit, then move, otherwise don't + * bother here either. + */ + if (fit_target) + cpu = target; + } + } } out_unlock: -- 2.17.1
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