linux-kernel - [PATCH v2] sched: revise the initial value of the util

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Message-ID: <1604575253-2386-1-git-send-email-xuewen.yan@unisoc.com>
Date:   Thu, 5 Nov 2020 19:20:53 +0800
From:   Xuewen Yan <xuewen.yan@...soc.com>
To:     <mingo@...hat.com>, <peterz@...radead.org>,
        <juri.lelli@...hat.com>, <vincent.guittot@...aro.org>
CC:     <dietmar.eggemann@....com>, <rostedt@...dmis.org>,
        <bsegall@...gle.com>, <mgorman@...e.de>, <bristot@...hat.com>,
        <linux-kernel@...r.kernel.org>, <xuewen.yan94@...il.com>
Subject: [PATCH v2] sched: revise the initial value of the util_avg.

According to the original code logic:
                cfs_rq->avg.util_avg
sa->util_avg  = -------------------- * se->load.weight
                cfs_rq->avg.load_avg
but for fair_sched_class:
se->load.weight = 1024 * sched_prio_to_weight[prio];
        cfs_rq->avg.util_avg
so the  -------------------- must be extremely small, the
        cfs_rq->avg.load_avg
judgment condition "sa->util_avg < cap" could be established.
It's not fair for those tasks who has smaller nice value.

Signed-off-by: Xuewen Yan <xuewen.yan@...soc.com>
---
 kernel/sched/fair.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 290f9e3..079760b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -794,7 +794,11 @@ void post_init_entity_util_avg(struct task_struct *p)

        if (cap > 0) {
                if (cfs_rq->avg.util_avg != 0) {
-                       sa->util_avg  = cfs_rq->avg.util_avg * se->load.weight;
+                       if (p->sched_class == &fair_sched_class)
+                               sa->util_avg  = cfs_rq->avg.util_avg * se_weight(se);
+                       else
+                               sa->util_avg  = cfs_rq->avg.util_avg * se->load.weight;
+
                        sa->util_avg /= (cfs_rq->avg.load_avg + 1);

                        if (sa->util_avg > cap)
--
1.9.1

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