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Message-ID: <1427741729.5694.24.camel@j-VirtualBox>
Date: Mon, 30 Mar 2015 11:55:29 -0700
From: Jason Low <jason.low2@...com>
To: Preeti U Murthy <preeti@...ux.vnet.ibm.com>, peterz@...radead.org,
mingo@...nel.org, Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: riel@...hat.com, daniel.lezcano@...aro.org,
vincent.guittot@...aro.org, srikar@...ux.vnet.ibm.com,
pjt@...gle.com, benh@...nel.crashing.org, efault@....de,
linux-kernel@...r.kernel.org, iamjoonsoo.kim@....com,
svaidy@...ux.vnet.ibm.com, tim.c.chen@...ux.intel.com,
morten.rasmussen@....com, jason.low2@...com
Subject: sched: Improve load balancing in the presence of idle CPUs
Hi Preeti,
I noticed that another commit 4a725627f21d converted the check in
nohz_kick_needed() from idle_cpu() to rq->idle_balance, causing a
potentially outdated value to be used if this cpu is able to pull tasks
using rebalance_domains(), and nohz_kick_needed() directly returning
false.
Would this patch also help address some of the issue you are seeing?
Signed-off-by: Jason Low <jason.low2@...com>
---
kernel/sched/fair.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index fdae26e..ba8ec1a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7644,7 +7644,7 @@ static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
* balancing owner will pick it up.
*/
if (need_resched())
- break;
+ goto end;
rq = cpu_rq(balance_cpu);
@@ -7687,7 +7687,7 @@ static inline bool nohz_kick_needed(struct rq *rq)
int nr_busy, cpu = rq->cpu;
bool kick = false;
- if (unlikely(rq->idle_balance))
+ if (unlikely(idle_cpu(cpu)))
return false;
/*
--
1.7.2.5
--
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