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sched: Add /debug/sched_preempt

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

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/YAsGiUYf6NyaTplX@hirez.programming.kicks-ass.net
This commit is contained in:
Peter Zijlstra 2021-01-22 13:01:58 +01:00 committed by Ingo Molnar
parent 826bfeb37b
commit e59e10f8ef
1 changed files with 126 additions and 9 deletions
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135
kernel/sched/core.c
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@ -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 */