Messages in this thread Patch in this message | | | Date | Tue, 27 Mar 2012 08:35:59 -0700 | From | tip-bot for Michael J Wang <> | Subject | [tip:sched/urgent] sched/rt: Improve pick_next_highest_task_rt() |
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Commit-ID: 1b028abc779b67b699daff55e27d2432f8d92666 Gitweb: http://git.kernel.org/tip/1b028abc779b67b699daff55e27d2432f8d92666 Author: Michael J Wang <mjwang@broadcom.com> AuthorDate: Mon, 19 Mar 2012 22:26:19 +0000 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Tue, 27 Mar 2012 14:52:12 +0200
sched/rt: Improve pick_next_highest_task_rt()
Avoid extra work by continuing on to the next rt_rq if the highest prio task in current rt_rq is the same priority as our candidate task.
More detailed explanation: if next is not NULL, then we have found a candidate task, and its priority is next->prio. Now we are looking for an even higher priority task in the other rt_rq's. idx is the highest priority in the current candidate rt_rq. In the current 3.3 code, if idx is equal to next->prio, we would start scanning the tasks in that rt_rq and replace the current candidate task with a task from that rt_rq. But the new task would only have a priority that is equal to our previous candidate task, so we have not advanced our goal of finding a higher prio task. So we should avoid the extra work by continuing on to the next rt_rq if idx is equal to next->prio.
Signed-off-by: Michael J Wang <mjwang@broadcom.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Reviewed-by: Yong Zhang <yong.zhang0@gmail.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/2EF88150C0EF2C43A218742ED384C1BC0FC83D6B@IRVEXCHMB08.corp.ad.broadcom.com Signed-off-by: Ingo Molnar <mingo@kernel.org> --- kernel/sched/rt.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index b60dad7..44af55e 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1428,7 +1428,7 @@ static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu) next_idx: if (idx >= MAX_RT_PRIO) continue; - if (next && next->prio < idx) + if (next && next->prio <= idx) continue; list_for_each_entry(rt_se, array->queue + idx, run_list) { struct task_struct *p;
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