Messages in this thread Patch in this message | | | Subject | [PATCH] sched-rt: Reduce rq lock contention by eliminating locking of non-feasible target | From | Tim Chen <> | Date | Wed, 17 Dec 2014 17:23:33 -0800 |
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This patch added checks that prevent futile attempts to move rt tasks to cpu with active tasks of equal or higher priority. This reduces run queue lock contention and improves the performance of a well known OLTP benchmark by 0.7%.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> --- kernel/sched/rt.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index ee15f5a..0e4382e 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1337,7 +1337,8 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags) curr->prio <= p->prio)) { int target = find_lowest_rq(p); - if (target != -1) + if (target != -1 && + p->prio < cpu_rq(target)->rt.highest_prio.curr) cpu = target; } rcu_read_unlock(); @@ -1613,6 +1614,12 @@ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq) break; lowest_rq = cpu_rq(cpu); + + if (lowest_rq->rt.highest_prio.curr <= task->prio) { + /* target rq has tasks of equal or higher priority, try again */ + lowest_rq = NULL; + continue; + } /* if the prio of this runqueue changed, try again */ if (double_lock_balance(rq, lowest_rq)) { -- 1.8.3.1
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