Messages in this thread Patch in this message | | | Subject | RE: [PATCH 1/1] scheduler: minor improvement to pick_next_highest_task_rt in linux-3.3 | From | Peter Zijlstra <> | Date | Wed, 21 Mar 2012 10:06:59 +0100 |
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On Wed, 2012-03-21 at 07:49 +0000, Michael J. Wang wrote: > > > Should I reformat my patch and send it again? > > > > It'll be better, and I think Peter/Ingo will happy with it. > > > > OK. I will resend now. Thanks for all your help!
The resend didn't include the more details thing, so I fudged it by hand. The queued thing now looks like this:
--- Subject: sched, rt: Minor improvement to pick_next_highest_task_rt From: Michael J Wang <mjwang@broadcom.com> Date: Mon, 19 Mar 2012 22:26:19 +0000
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 --- kernel/sched/rt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1428,7 +1428,7 @@ static struct task_struct *pick_next_hig 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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