linux-kernel - [PATCH] sched/rt: Add borrowing time condition

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Date:   Wed, 20 May 2020 16:09:11 +0800
From:   <qiang.zhang@...driver.com>
To:     <mingo@...hat.com>, <peterz@...radead.org>,
        <juri.lelli@...hat.com>, <vincent.guittot@...aro.org>,
        <dietmar.eggemann@....com>, <rostedt@...dmis.org>,
        <bsegall@...gle.com>, <mgorman@...e.de>
CC:     <linux-kernel@...r.kernel.org>
Subject: [PATCH] sched/rt: Add borrowing time condition

From: Zhang Qiang <qiang.zhang@...driver.com>

Add priority judgment to determine whether to borrow time from neighbors,
ensure that the rt_runntime of rt_rq with higher priority tasks is not
reduced

Signed-off-by: Zhang Qiang <qiang.zhang@...driver.com>
---
 kernel/sched/rt.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 4043abe45459..d2a1acad6687 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -711,8 +711,10 @@ static void do_balance_runtime(struct rt_rq *rt_rq)
 			diff = div_u64((u64)diff, weight);
 			if (rt_rq->rt_runtime + diff > rt_period)
 				diff = rt_period - rt_rq->rt_runtime;
-			iter->rt_runtime -= diff;
-			rt_rq->rt_runtime += diff;
+			if (rt_rq->highest_prio.curr < iter->highest_prio.curr) {
+				iter->rt_runtime -= diff;
+				rt_rq->rt_runtime += diff;
+			}
 			if (rt_rq->rt_runtime == rt_period) {
 				raw_spin_unlock(&iter->rt_runtime_lock);
 				break;
-- 
2.17.0