linux-kernel - check_preempt_tick() check vruntime mistake?

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Date:	Fri, 11 Dec 2009 12:17:50 +0800
From:	XingChao Wang <wxc200@...il.com>
To:	kernel list <linux-kernel@...r.kernel.org>
Cc:	mingo@...e.hu, Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: check_preempt_tick() check vruntime mistake?

Hi Ingo,peter,

When check_preempt_tick() selects next leftmost sched_entity,it
calculates delta vruntime of curr and leftmost entity, then compares
it with ideal_runtime. But ideal_runtime is real-time type, need
convert it to virtual-time ,right?

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 37087a7..9b903d4 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -840,7 +840,7 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct
sched_entity *curr)
                struct sched_entity *se = __pick_next_entity(cfs_rq);
                s64 delta = curr->vruntime - se->vruntime;

-               if (delta > ideal_runtime)
+               if (delta > calc_delta_fair(ideal_runtime, curr))
                        resched_task(rq_of(cfs_rq)->curr);
        }
 }

thanks
--wang xingchao
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