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Message-ID: <tip-444969223c81c7d0a95136b7b4cfdcfbc96ac5bd@git.kernel.org>
Date: Thu, 12 May 2016 03:31:04 -0700
From: tip-bot for Wanpeng Li <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: fweisbec@...il.com, peterz@...radead.org, efault@....de,
tglx@...utronix.de, torvalds@...ux-foundation.org,
linux-kernel@...r.kernel.org, mingo@...nel.org, hpa@...or.com,
wanpeng.li@...mail.com
Subject: [tip:sched/core] sched/nohz: Fix affine unpinned timers mess
Commit-ID: 444969223c81c7d0a95136b7b4cfdcfbc96ac5bd
Gitweb: http://git.kernel.org/tip/444969223c81c7d0a95136b7b4cfdcfbc96ac5bd
Author: Wanpeng Li <wanpeng.li@...mail.com>
AuthorDate: Wed, 4 May 2016 14:45:34 +0800
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 12 May 2016 09:55:32 +0200
sched/nohz: Fix affine unpinned timers mess
The following commit:
9642d18eee2c ("nohz: Affine unpinned timers to housekeepers")'
intended to affine unpinned timers to housekeepers:
unpinned timers(full dynaticks, idle) => nearest busy housekeepers(otherwise, fallback to any housekeepers)
unpinned timers(full dynaticks, busy) => nearest busy housekeepers(otherwise, fallback to any housekeepers)
unpinned timers(houserkeepers, idle) => nearest busy housekeepers(otherwise, fallback to itself)
However, the !idle_cpu(i) && is_housekeeping_cpu(cpu) check modified the
intention to:
unpinned timers(full dynaticks, idle) => any housekeepers(no mattter cpu topology)
unpinned timers(full dynaticks, busy) => any housekeepers(no mattter cpu topology)
unpinned timers(housekeepers, idle) => any busy cpus(otherwise, fallback to any housekeepers)
This patch fixes it by checking if there are busy housekeepers nearby,
otherwise falls to any housekeepers/itself. After the patch:
unpinned timers(full dynaticks, idle) => nearest busy housekeepers(otherwise, fallback to any housekeepers)
unpinned timers(full dynaticks, busy) => nearest busy housekeepers(otherwise, fallback to any housekeepers)
unpinned timers(housekeepers, idle) => nearest busy housekeepers(otherwise, fallback to itself)
Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
[ Fixed the changelog. ]
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org
Fixes: 'commit 9642d18eee2c ("nohz: Affine unpinned timers to housekeepers")'
Link: http://lkml.kernel.org/r/1462344334-8303-1-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
kernel/sched/core.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 636c4b9..6f6962a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -533,7 +533,10 @@ int get_nohz_timer_target(void)
rcu_read_lock();
for_each_domain(cpu, sd) {
for_each_cpu(i, sched_domain_span(sd)) {
- if (!idle_cpu(i) && is_housekeeping_cpu(cpu)) {
+ if (cpu == i)
+ continue;
+
+ if (!idle_cpu(i) && is_housekeeping_cpu(i)) {
cpu = i;
goto unlock;
}
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