Re: [patch 06/16] sched: add notifier for cross-cpu migrations

[Glauber Costa <glommer@parallels.com>]

On 11/01/2012 02:47 AM, Marcelo Tosatti wrote:
> Originally from Jeremy Fitzhardinge.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 

Please collect peterz's ack for this one.

> Index: vsyscall/include/linux/sched.h
> ===================================================================
> --- vsyscall.orig/include/linux/sched.h
> +++ vsyscall/include/linux/sched.h
> @@ -107,6 +107,14 @@ extern unsigned long this_cpu_load(void)
>  extern void calc_global_load(unsigned long ticks);
>  extern void update_cpu_load_nohz(void);
>  
> +/* Notifier for when a task gets migrated to a new CPU */
> +struct task_migration_notifier {
> +	struct task_struct *task;
> +	int from_cpu;
> +	int to_cpu;
> +};
> +extern void register_task_migration_notifier(struct notifier_block *n);
> +
>  extern unsigned long get_parent_ip(unsigned long addr);
>  
>  struct seq_file;
> Index: vsyscall/kernel/sched/core.c
> ===================================================================
> --- vsyscall.orig/kernel/sched/core.c
> +++ vsyscall/kernel/sched/core.c
> @@ -922,6 +922,13 @@ void check_preempt_curr(struct rq *rq, s
>  		rq->skip_clock_update = 1;
>  }
>  
> +static ATOMIC_NOTIFIER_HEAD(task_migration_notifier);
> +
> +void register_task_migration_notifier(struct notifier_block *n)
> +{
> +	atomic_notifier_chain_register(&task_migration_notifier, n);
> +}
> +
>  #ifdef CONFIG_SMP
>  void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
>  {
> @@ -952,8 +959,16 @@ void set_task_cpu(struct task_struct *p,
>  	trace_sched_migrate_task(p, new_cpu);
>  
>  	if (task_cpu(p) != new_cpu) {
> +		struct task_migration_notifier tmn;
> +
>  		p->se.nr_migrations++;
>  		perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS, 1, NULL, 0);
> +
> +		tmn.task = p;
> +		tmn.from_cpu = task_cpu(p);
> +		tmn.to_cpu = new_cpu;
> +
> +		atomic_notifier_call_chain(&task_migration_notifier, 0, &tmn);
>  	}
>  
>  	__set_task_cpu(p, new_cpu);
> 
>