Commit e59e10f8 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Add /debug/sched_preempt 



Add a debugfs file to muck about with the preempt mode at runtime.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/YAsGiUYf6NyaTplX@hirez.programming.kicks-ass.net
parent 826bfeb3

kernel/sched/core.c

+126 −9
Original line number Diff line number Diff line
@@ -5363,37 +5363,154 @@ EXPORT_STATIC_CALL(preempt_schedule_notrace); 
 *   preempt_schedule_notrace   <- preempt_schedule_notrace

 *   irqentry_exit_cond_resched <- irqentry_exit_cond_resched

 */

static int __init setup_preempt_mode(char *str)



enum {

	preempt_dynamic_none = 0,

	preempt_dynamic_voluntary,

	preempt_dynamic_full,

};



static int preempt_dynamic_mode = preempt_dynamic_full;



static int sched_dynamic_mode(const char *str)

{

	if (!strcmp(str, "none")) {

	if (!strcmp(str, "none"))

		return 0;



	if (!strcmp(str, "voluntary"))

		return 1;



	if (!strcmp(str, "full"))

		return 2;



	return -1;

}



static void sched_dynamic_update(int mode)

{

	/*

	 * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in

	 * the ZERO state, which is invalid.

	 */

	static_call_update(cond_resched, __cond_resched);

	static_call_update(might_resched, __cond_resched);

	static_call_update(preempt_schedule, __preempt_schedule_func);

	static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func);

	static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched);



	switch (mode) {

	case preempt_dynamic_none:

		static_call_update(cond_resched, __cond_resched);

		static_call_update(might_resched, (typeof(&__cond_resched)) __static_call_return0);

		static_call_update(preempt_schedule, (typeof(&preempt_schedule)) NULL);

		static_call_update(preempt_schedule_notrace, (typeof(&preempt_schedule_notrace)) NULL);

		static_call_update(irqentry_exit_cond_resched, (typeof(&irqentry_exit_cond_resched)) NULL);

		pr_info("Dynamic Preempt: %s\n", str);

	} else if (!strcmp(str, "voluntary")) {

		pr_info("Dynamic Preempt: none\n");

		break;



	case preempt_dynamic_voluntary:

		static_call_update(cond_resched, __cond_resched);

		static_call_update(might_resched, __cond_resched);

		static_call_update(preempt_schedule, (typeof(&preempt_schedule)) NULL);

		static_call_update(preempt_schedule_notrace, (typeof(&preempt_schedule_notrace)) NULL);

		static_call_update(irqentry_exit_cond_resched, (typeof(&irqentry_exit_cond_resched)) NULL);

		pr_info("Dynamic Preempt: %s\n", str);

	} else if (!strcmp(str, "full")) {

		pr_info("Dynamic Preempt: voluntary\n");

		break;



	case preempt_dynamic_full:

		static_call_update(cond_resched, (typeof(&__cond_resched)) __static_call_return0);

		static_call_update(might_resched, (typeof(&__cond_resched)) __static_call_return0);

		static_call_update(preempt_schedule, __preempt_schedule_func);

		static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func);

		static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched);

		pr_info("Dynamic Preempt: %s\n", str);

	} else {

		pr_warn("Dynamic Preempt: Unsupported preempt mode %s, default to full\n", str);

		pr_info("Dynamic Preempt: full\n");

		break;

	}



	preempt_dynamic_mode = mode;

}



static int __init setup_preempt_mode(char *str)

{

	int mode = sched_dynamic_mode(str);

	if (mode < 0) {

		pr_warn("Dynamic Preempt: unsupported mode: %s\n", str);

		return 1;

	}



	sched_dynamic_update(mode);

	return 0;

}

__setup("preempt=", setup_preempt_mode);



#ifdef CONFIG_SCHED_DEBUG



static ssize_t sched_dynamic_write(struct file *filp, const char __user *ubuf,

				   size_t cnt, loff_t *ppos)

{

	char buf[16];

	int mode;



	if (cnt > 15)

		cnt = 15;



	if (copy_from_user(&buf, ubuf, cnt))

		return -EFAULT;



	buf[cnt] = 0;

	mode = sched_dynamic_mode(strstrip(buf));

	if (mode < 0)

		return mode;



	sched_dynamic_update(mode);



	*ppos += cnt;



	return cnt;

}



static int sched_dynamic_show(struct seq_file *m, void *v)

{

	static const char * preempt_modes[] = {

		"none", "voluntary", "full"

	};

	int i;



	for (i = 0; i < ARRAY_SIZE(preempt_modes); i++) {

		if (preempt_dynamic_mode == i)

			seq_puts(m, "(");

		seq_puts(m, preempt_modes[i]);

		if (preempt_dynamic_mode == i)

			seq_puts(m, ")");



		seq_puts(m, " ");

	}



	seq_puts(m, "\n");

	return 0;

}



static int sched_dynamic_open(struct inode *inode, struct file *filp)

{

	return single_open(filp, sched_dynamic_show, NULL);

}



static const struct file_operations sched_dynamic_fops = {

	.open		= sched_dynamic_open,

	.write		= sched_dynamic_write,

	.read		= seq_read,

	.llseek		= seq_lseek,

	.release	= single_release,

};



static __init int sched_init_debug_dynamic(void)

{

	debugfs_create_file("sched_preempt", 0644, NULL, NULL, &sched_dynamic_fops);

	return 0;

}

late_initcall(sched_init_debug_dynamic);



#endif /* CONFIG_SCHED_DEBUG */

#endif /* CONFIG_PREEMPT_DYNAMIC */