Re: [PATCH] vmstat: on demand updates from differentials V7

[Frederic Weisbecker <fweisbec@gmail.com>]

On Thu, May 29, 2014 at 02:56:15PM -0500, Christoph Lameter wrote:
> 
> -static void start_cpu_timer(int cpu)
> +static void __init start_shepherd_timer(void)
>  {
> -	struct delayed_work *work = &per_cpu(vmstat_work, cpu);
> +	int cpu;
> +
> +	for_each_possible_cpu(cpu)
> +		INIT_DEFERRABLE_WORK(per_cpu_ptr(&vmstat_work, cpu),
> +			vmstat_update);
> +
> +	cpu_stat_off = kmalloc(cpumask_size(), GFP_KERNEL);
> +	cpumask_copy(cpu_stat_off, cpu_online_mask);

Actually looks like you can as well remove that cpumask and use
cpu_online_mask directly.

> 
> -	INIT_DEFERRABLE_WORK(work, vmstat_update);
> -	schedule_delayed_work_on(cpu, work, __round_jiffies_relative(HZ, cpu));
> +	schedule_delayed_work(&shepherd,
> +		round_jiffies_relative(sysctl_stat_interval));
>  }
> 
>  static void vmstat_cpu_dead(int node)
> @@ -1266,17 +1367,17 @@
>  	case CPU_ONLINE:
>  	case CPU_ONLINE_FROZEN:
>  		refresh_zone_stat_thresholds();
> -		start_cpu_timer(cpu);
>  		node_set_state(cpu_to_node(cpu), N_CPU);
> +		cpumask_set_cpu(cpu, cpu_stat_off);
>  		break;
>  	case CPU_DOWN_PREPARE:
>  	case CPU_DOWN_PREPARE_FROZEN:
> -		cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
> -		per_cpu(vmstat_work, cpu).work.func = NULL;
> +		if (!cpumask_test_and_set_cpu(cpu, cpu_stat_off))
> +			cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
>  		break;
>  	case CPU_DOWN_FAILED:
>  	case CPU_DOWN_FAILED_FROZEN:
> -		start_cpu_timer(cpu);
> +		cpumask_set_cpu(cpu, cpu_stat_off);
>  		break;
>  	case CPU_DEAD:
>  	case CPU_DEAD_FROZEN:
> @@ -1296,15 +1397,10 @@
>  static int __init setup_vmstat(void)
>  {
>  #ifdef CONFIG_SMP
> -	int cpu;
> -
>  	cpu_notifier_register_begin();
>  	__register_cpu_notifier(&vmstat_notifier);
> 
> -	for_each_online_cpu(cpu) {
> -		start_cpu_timer(cpu);
> -		node_set_state(cpu_to_node(cpu), N_CPU);
> -	}
> +	start_shepherd_timer();
>  	cpu_notifier_register_done();
>  #endif
>  #ifdef CONFIG_PROC_FS

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