The following commit has been merged into the timers/core branch of tip:
Commit-ID: 96f9a366ec8abe027326d7aab84d64370019f0f1
Gitweb: https://git.kernel.org/tip/96f9a366ec8abe027326d7aab84d64370019f0f1
Author: Jeff Layton <jlayton@xxxxxxxxxx>
AuthorDate: Wed, 02 Oct 2024 17:27:17 -04:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Sun, 06 Oct 2024 20:56:07 +02:00
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: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> # documentation bits
Link: https://lore.kernel.org/all/20241002-mgtime-v10-2-d1c4717f5284@xxxxxxxxxx
---
include/linux/timekeeping.h | 1 +
kernel/time/timekeeping.c | 1 +
kernel/time/timekeeping_debug.c | 13 +++++++++++++
kernel/time/timekeeping_internal.h | 15 +++++++++++++++
4 files changed, 30 insertions(+)
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 7aa8524..84a035e 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -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);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 441792c..962b2a3 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -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.
diff --git a/kernel/time/timekeeping_debug.c b/kernel/time/timekeeping_debug.c
index b73e885..badeb22 100644
--- a/kernel/time/timekeeping_debug.c
+++ b/kernel/time/timekeeping_debug.c
@@ -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;
+}
diff --git a/kernel/time/timekeeping_internal.h b/kernel/time/timekeeping_internal.h
index 4ca2787..0bbae82 100644
--- a/kernel/time/timekeeping_internal.h
+++ b/kernel/time/timekeeping_internal.h
@@ -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
|