Messages in this thread Patch in this message | | | From | Wanpeng Li <> | Subject | [PATCH] sched/nohz: fix affine unpinned timers mess | Date | Wed, 4 May 2016 14:45:34 +0800 |
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From: Wanpeng Li <wanpeng.li@hotmail.com>
'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 modify 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 fix it by checking if there is busy housekeepers nearby, otherwise fallback 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)
Fixes: 'commit 9642d18eee2c ("nohz: Affine unpinned timers to housekeepers")' Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> --- kernel/sched/core.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index adcafda..5538761 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -499,7 +499,10 @@ 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; } -- 1.7.1
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