Commit 96f9a366 authored by Jeff Layton's avatar Jeff Layton Committed by Thomas Gleixner
Browse files

timekeeping: Add percpu counter for tracking floor swap events 



The mgtime_floor value is a global variable for tracking the latest
fine-grained timestamp handed out. Because it's a global, track the
number of times that a new floor value is assigned.

Add a new percpu counter to the timekeeping code to track the number of
floor swap events that have occurred. A later patch will add a debugfs
file to display this counter alongside other stats involving multigrain
timestamps.

Signed-off-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # documentation bits
Link: https://lore.kernel.org/all/20241002-mgtime-v10-2-d1c4717f5284@kernel.org
parent 70c8fd00

include/linux/timekeeping.h

+1 −0
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ extern void ktime_get_coarse_real_ts64(struct timespec64 *ts); 
/* Multigrain timestamp interfaces */

extern void ktime_get_coarse_real_ts64_mg(struct timespec64 *ts);

extern void ktime_get_real_ts64_mg(struct timespec64 *ts);

extern unsigned long timekeeping_get_mg_floor_swaps(void);



void getboottime64(struct timespec64 *ts);

kernel/time/timekeeping.c

+1 −0
Original line number Diff line number Diff line
@@ -2487,6 +2487,7 @@ void ktime_get_real_ts64_mg(struct timespec64 *ts) 
	if (atomic64_try_cmpxchg(&mg_floor, &old, mono)) {

		ts->tv_nsec = 0;

		timespec64_add_ns(ts, nsecs);

		timekeeping_inc_mg_floor_swaps();

	} else {

		/*

		 * Another task changed mg_floor since "old" was fetched.

kernel/time/timekeeping_debug.c

+13 −0
Original line number Diff line number Diff line
@@ -17,6 +17,9 @@ 


#define NUM_BINS 32



/* Incremented every time mg_floor is updated */

DEFINE_PER_CPU(unsigned long, timekeeping_mg_floor_swaps);



static unsigned int sleep_time_bin[NUM_BINS] = {0};



static int tk_debug_sleep_time_show(struct seq_file *s, void *data)
@@ -53,3 +56,13 @@ void tk_debug_account_sleep_time(const struct timespec64 *t) 
			   (s64)t->tv_sec, t->tv_nsec / NSEC_PER_MSEC);

}



unsigned long timekeeping_get_mg_floor_swaps(void)

{

	unsigned long sum = 0;

	int cpu;



	for_each_possible_cpu(cpu)

		sum += data_race(per_cpu(timekeeping_mg_floor_swaps, cpu));



	return sum;

}

kernel/time/timekeeping_internal.h

+15 −0
Original line number Diff line number Diff line
@@ -10,9 +10,24 @@ 
 * timekeeping debug functions

 */

#ifdef CONFIG_DEBUG_FS



DECLARE_PER_CPU(unsigned long, timekeeping_mg_floor_swaps);



static inline void timekeeping_inc_mg_floor_swaps(void)

{

	this_cpu_inc(timekeeping_mg_floor_swaps);

}



extern void tk_debug_account_sleep_time(const struct timespec64 *t);



#else



#define tk_debug_account_sleep_time(x)



static inline void timekeeping_inc_mg_floor_swaps(void)

{

}



#endif



#ifdef CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE