Commit 5f8e3202 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcuscale: Measure grace-period kthread CPU time 



This commit adds the ability to output the CPU time consumed by the
grace-period kthread for the RCU variant under test.  The CPU time is
whatever is in the designated task's current->stime field, and thus is
controlled by whatever CPU-time accounting scheme is in effect.

This output appears in microseconds as follows on the console:

rcu_scale: Grace-period kthread CPU time: 42367.037

[ paulmck: Apply feedback from Stephen Rothwell and kernel test robot. ]

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Tested-by: default avatarYujie Liu <yujie.liu@intel.com>
parent bb7bad3d

include/linux/rcupdate_trace.h

+1 −0
Original line number Diff line number Diff line
@@ -87,6 +87,7 @@ static inline void rcu_read_unlock_trace(void) 
void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func);

void synchronize_rcu_tasks_trace(void);

void rcu_barrier_tasks_trace(void);

struct task_struct *get_rcu_tasks_trace_gp_kthread(void);

#else

/*

 * The BPF JIT forms these addresses even when it doesn't call these

kernel/rcu/rcuscale.c

+21 −0
Original line number Diff line number Diff line
@@ -141,6 +141,7 @@ struct rcu_scale_ops { 
	void (*gp_barrier)(void);

	void (*sync)(void);

	void (*exp_sync)(void);

	struct task_struct *(*rso_gp_kthread)(void);

	const char *name;

};
@@ -336,6 +337,7 @@ static struct rcu_scale_ops tasks_tracing_ops = { 
	.gp_barrier	= rcu_barrier_tasks_trace,

	.sync		= synchronize_rcu_tasks_trace,

	.exp_sync	= synchronize_rcu_tasks_trace,

	.rso_gp_kthread	= get_rcu_tasks_trace_gp_kthread,

	.name		= "tasks-tracing"

};
@@ -563,6 +565,8 @@ static struct task_struct **kfree_reader_tasks; 
static int kfree_nrealthreads;

static atomic_t n_kfree_scale_thread_started;

static atomic_t n_kfree_scale_thread_ended;

static struct task_struct *kthread_tp;

static u64 kthread_stime;



struct kfree_obj {

	char kfree_obj[8];
@@ -808,6 +812,18 @@ rcu_scale_cleanup(void) 
	if (gp_exp && gp_async)

		SCALEOUT_ERRSTRING("No expedited async GPs, so went with async!");



	// If built-in, just report all of the GP kthread's CPU time.

	if (IS_BUILTIN(CONFIG_RCU_SCALE_TEST) && !kthread_tp && cur_ops->rso_gp_kthread)

		kthread_tp = cur_ops->rso_gp_kthread();

	if (kthread_tp) {

		u32 ns;

		u64 us;



		kthread_stime = kthread_tp->stime - kthread_stime;

		us = div_u64_rem(kthread_stime, 1000, &ns);

		pr_info("rcu_scale: Grace-period kthread CPU time: %llu.%03u us\n", us, ns);

		show_rcu_gp_kthreads();

	}

	if (kfree_rcu_test) {

		kfree_scale_cleanup();

		return;
@@ -921,6 +937,11 @@ rcu_scale_init(void) 
	if (cur_ops->init)

		cur_ops->init();



	if (cur_ops->rso_gp_kthread) {

		kthread_tp = cur_ops->rso_gp_kthread();

		if (kthread_tp)

			kthread_stime = kthread_tp->stime;

	}

	if (kfree_rcu_test)

		return kfree_scale_init();

kernel/rcu/tasks.h

+6 −0
Original line number Diff line number Diff line
@@ -1830,6 +1830,12 @@ void show_rcu_tasks_trace_gp_kthread(void) 
EXPORT_SYMBOL_GPL(show_rcu_tasks_trace_gp_kthread);

#endif // !defined(CONFIG_TINY_RCU)



struct task_struct *get_rcu_tasks_trace_gp_kthread(void)

{

	return rcu_tasks_trace.kthread_ptr;

}

EXPORT_SYMBOL_GPL(get_rcu_tasks_trace_gp_kthread);



#else /* #ifdef CONFIG_TASKS_TRACE_RCU */

static void exit_tasks_rcu_finish_trace(struct task_struct *t) { }

#endif /* #else #ifdef CONFIG_TASKS_TRACE_RCU */