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Date: Mon, 17 Sep 2012 16:54:19 +0800 From: Xiong Wu <xiong.wu1981@...il.com> To: linux-kernel@...r.kernel.org Subject: Side effects of disabling SCHED_SOFTIRQ to trigger run_rebalance_domains Hi all, Since observed dead lock problem in sched run_rebalance_domains of kernel 2.6.21.7, we just disabling SCHED_SOFTIRQ to trigger run_rebalance_domains as one work around. The patch is as below: --- kernel/sched.c 2012-06-29 23:17:34.000000000 +0800 +++ kernel-new/sched.c 2012-09-12 17:27:28.000000000 +0800 @@ -2940,7 +2940,7 @@ static void update_load(struct rq *this_ * Balancing parameters are set up in arch_init_sched_domains. */ static DEFINE_SPINLOCK(balancing); - +#if 0 static void run_rebalance_domains(struct softirq_action *h) { int this_cpu = smp_processor_id(), balance = 1; @@ -3001,6 +3001,7 @@ out: } this_rq->next_balance = next_balance; } +#endif #else /* * on UP we do not need to balance between CPUs: @@ -3230,9 +3231,11 @@ void scheduler_tick(void) task_running_tick(rq, p); #ifdef CONFIG_SMP update_load(rq); +#if 0 if (time_after_eq(jiffies, rq->next_balance)) raise_softirq(SCHED_SOFTIRQ); #endif +#endif } #if defined(CONFIG_PREEMPT) && defined(CONFIG_DEBUG_PREEMPT) @@ -6766,9 +6769,11 @@ void __init sched_init(void) set_load_weight(&init_task); +#if 0 #ifdef CONFIG_SMP open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL); #endif +#endif #ifdef CONFIG_RT_MUTEXES plist_head_init(&init_task.pi_waiters, &init_task.pi_lock); Our experimentations and simulations that we have conducted so far did not indicated any performance decrease due to disable re-balancing. Since our system isn't always busy, the idle_balance can work well for processes load balance instead of run_rebalance_domains. However my concern is if there is any side effects which I didn't consider. Thanks, Xiong -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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