linux-kernel - [PATCH] sched/fair: Fix negative imbalance in imbalance calculation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <1585201349-70192-1-git-send-email-aubrey.li@intel.com>
Date:   Thu, 26 Mar 2020 13:42:29 +0800
From:   Aubrey Li <aubrey.li@...el.com>
To:     vincent.guittot@...aro.org, mingo@...hat.com, peterz@...radead.org,
        juri.lelli@...hat.com, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        linux-kernel@...r.kernel.org
Cc:     tim.c.chen@...ux.intel.com, vpillai@...italocean.com,
        joel@...lfernandes.org, Aubrey Li <aubrey.li@...el.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Phil Auld <pauld@...hat.com>
Subject: [PATCH] sched/fair: Fix negative imbalance in imbalance calculation

A negative imbalance value was observed after imbalance calculation,
this happens when the local sched group type is group_fully_busy,
and the average load of local group is greater than the selected
busiest group. Fix this problem by comparing the average load of the
local and busiest group before imbalance calculation formula.

Suggested-by: Vincent Guittot <vincent.guittot@...aro.org>
Signed-off-by: Aubrey Li <aubrey.li@...ux.intel.com>
Cc: Phil Auld <pauld@...hat.com>
---
 kernel/sched/fair.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c1217bf..4a2ba3f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8761,6 +8761,14 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
 
 		sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) /
 				sds->total_capacity;
+		/*
+		 * If the local group is more loaded than the selected
+		 * busiest group don't try to pull any tasks.
+		 */
+		if (local->avg_load >= busiest->avg_load) {
+			env->imbalance = 0;
+			return;
+		}
 	}
 
 	/*
-- 
2.7.4