ck-hrtimer-0008.patch

From 308a45413e82f6be1bf10864f5f9eab6bf0dd799 Mon Sep 17 00:00:00 2001
From: graysky <therealgraysky@proton.me>
Date: Wed, 5 Oct 2022 05:45:01 -0400
Subject: [PATCH 8/8] clockevents, hrtimer: Make hrtimer granularity and
 minimum hrtimeout configurable in sysctl. Set default granularity to 100us 
 and min timeout to 500us

---
 kernel/sysctl.c           | 21 +++++++++++++++++
 kernel/time/clockevents.c |  3 ++-
 kernel/time/hrtimer.c     | 49 +++++++++++++++++++++++++++++++++++----
 3 files changed, 68 insertions(+), 5 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c6d9dec11b74..1c806db94b22 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -92,6 +92,9 @@ EXPORT_SYMBOL_GPL(sysctl_long_vals);
 #if defined(CONFIG_SYSCTL)
 
 /* Constants used for minimum and maximum */
+static int ten_thousand = 10000;
+extern int hrtimer_granularity_us;
+extern int hrtimeout_min_us;
 
 #ifdef CONFIG_PERF_EVENTS
 static const int six_hundred_forty_kb = 640 * 1024;
@@ -1642,6 +1642,24 @@
 
 static struct ctl_table kern_table[] = {
 	{
+		.procname       = "hrtimer_granularity_us",
+		.data           = &hrtimer_granularity_us,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = &proc_dointvec_minmax,
+		.extra1         = SYSCTL_ONE,
+		.extra2         = &ten_thousand,
+	},
+	{
+		.procname       = "hrtimeout_min_us",
+		.data           = &hrtimeout_min_us,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = &proc_dointvec_minmax,
+		.extra1         = SYSCTL_ONE,
+		.extra2         = &ten_thousand,
+	},
+	{
 		.procname	= "panic",
 		.data		= &panic_timeout,
 		.maxlen		= sizeof(int),

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 5d85014d59b5..50406e057791 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -190,8 +190,9 @@ int clockevents_tick_resume(struct clock_event_device *dev)
 
 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
 
+int __read_mostly hrtimer_granularity_us = 100;
 /* Limit min_delta to a jiffie */
-#define MIN_DELTA_LIMIT		(NSEC_PER_SEC / HZ)
+#define MIN_DELTA_LIMIT		(hrtimer_granularity_us * NSEC_PER_USEC)
 
 /**
  * clockevents_increase_min_delta - raise minimum delta of a clock event device
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index f29c00e9709c..b2352612b8ea 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -2393,7 +2393,7 @@ EXPORT_SYMBOL_GPL(schedule_hrtimeout);
 long __sched schedule_msec_hrtimeout(long timeout)
 {
 	struct hrtimer_sleeper t;
-	int delta, secs, jiffs;
+	int delta, jiffs;
 	ktime_t expires;
 
 	if (!timeout) {
@@ -2410,9 +2410,8 @@ long __sched schedule_msec_hrtimeout(long timeout)
 	if (jiffs > 4 || hrtimer_resolution >= NSEC_PER_SEC / HZ || pm_freezing)
 		return schedule_timeout(jiffs);
 
-	secs = timeout / 1000;
 	delta = (timeout % 1000) * NSEC_PER_MSEC;
-	expires = ktime_set(secs, delta);
+	expires = ktime_set(0, delta);
 
 	hrtimer_init_sleeper_on_stack(&t, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	hrtimer_set_expires_range_ns(&t.timer, expires, delta);
@@ -2434,9 +2433,51 @@ long __sched schedule_msec_hrtimeout(long timeout)
 
 EXPORT_SYMBOL(schedule_msec_hrtimeout);
 
+#define USECS_PER_SEC 1000000
+extern int hrtimer_granularity_us;
+
+static inline long schedule_usec_hrtimeout(long timeout)
+{
+	struct hrtimer_sleeper t;
+	ktime_t expires;
+	int delta;
+
+	if (!timeout) {
+		__set_current_state(TASK_RUNNING);
+		return 0;
+	}
+
+	if (hrtimer_resolution >= NSEC_PER_SEC / HZ)
+		return schedule_timeout(usecs_to_jiffies(timeout));
+
+	if (timeout < hrtimer_granularity_us)
+		timeout = hrtimer_granularity_us;
+	delta = (timeout % USECS_PER_SEC) * NSEC_PER_USEC;
+	expires = ktime_set(0, delta);
+
+	hrtimer_init_sleeper_on_stack(&t, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	hrtimer_set_expires_range_ns(&t.timer, expires, delta);
+
+	hrtimer_sleeper_start_expires(&t, HRTIMER_MODE_REL);
+
+	if (likely(t.task))
+		schedule();
+
+	hrtimer_cancel(&t.timer);
+	destroy_hrtimer_on_stack(&t.timer);
+
+	__set_current_state(TASK_RUNNING);
+
+	expires = hrtimer_expires_remaining(&t.timer);
+	timeout = ktime_to_us(expires);
+	return timeout < 0 ? 0 : timeout;
+}
+
+int __read_mostly hrtimeout_min_us = 500;
+
 long __sched schedule_min_hrtimeout(void)
 {
-	return schedule_msec_hrtimeout(1);
+	return usecs_to_jiffies(schedule_usec_hrtimeout(hrtimeout_min_us));
 }
 
 EXPORT_SYMBOL(schedule_min_hrtimeout);
-- 
2.39.0