hfsc uses a scaled version of microseconds for time at the moment. it
seems more straightforward to just use nanoseconds.

kjc and cheloa like the idea. it seems to work fine in my own tests.

ok?

Index: hfsc.c
===================================================================
RCS file: /cvs/src/sys/net/hfsc.c,v
diff -u -p -r1.49 hfsc.c
--- hfsc.c	11 Apr 2023 00:45:09 -0000	1.49
+++ hfsc.c	30 Sep 2024 05:24:11 -0000
@@ -248,11 +248,12 @@ void		hfsc_rtsc_min(struct hfsc_runtime_
 void		hfsc_getclstats(struct hfsc_class_stats *, struct hfsc_class *);
 struct hfsc_class	*hfsc_clh2cph(struct hfsc_if *, u_int32_t);
 
-#define	HFSC_CLK_SHIFT		8
-#define	HFSC_FREQ		(1000000 << HFSC_CLK_SHIFT)
-#define	HFSC_CLK_PER_TICK	(HFSC_FREQ / hz)
+#define	HFSC_FREQ		1000000000LL
+#define	HFSC_CLK_PER_TICK	tick_nsec
 #define	HFSC_HT_INFINITY	0xffffffffffffffffLL /* infinite time value */
 
+#define hfsc_uptime()		nsecuptime()
+
 struct pool	hfsc_class_pl, hfsc_internal_sc_pl;
 
 /*
@@ -345,16 +346,6 @@ hfsc_class_purge(struct hfsc_class *cl, 
 		return cl->cl_qops->pfq_purge(cl->cl_qdata, ml);
 }
 
-u_int64_t
-hfsc_microuptime(void)
-{
-	struct timeval tv;
-
-	microuptime(&tv);
-	return (((u_int64_t)(tv.tv_sec) * 1000000 + tv.tv_usec) <<
-	    HFSC_CLK_SHIFT);
-}
-
 static inline u_int
 hfsc_more_slots(u_int current)
 {
@@ -845,7 +836,7 @@ hfsc_deq_begin(struct ifqueue *ifq, void
 	struct mbuf *m;
 	u_int64_t cur_time;
 
-	cur_time = hfsc_microuptime();
+	cur_time = hfsc_uptime();
 
 	/*
 	 * if there are eligible classes, use real-time criteria.
@@ -1007,7 +998,7 @@ hfsc_init_ed(struct hfsc_if *hif, struct
 {
 	u_int64_t cur_time;
 
-	cur_time = hfsc_microuptime();
+	cur_time = hfsc_uptime();
 
 	/* update the deadline curve */
 	hfsc_rtsc_min(&cl->cl_deadline, cl->cl_rsc, cur_time, cl->cl_cumul);
@@ -1114,7 +1105,7 @@ hfsc_init_vf(struct hfsc_class *cl, int 
 			if (cl->cl_usc != NULL) {
 				/* class has upper limit curve */
 				if (cur_time == 0)
-					cur_time = hfsc_microuptime();
+					cur_time = hfsc_uptime();
 
 				/* update the ulimit curve */
 				hfsc_rtsc_min(&cl->cl_ulimit, cl->cl_usc, cur_time,
@@ -1701,7 +1692,7 @@ hfsc_getclstats(struct hfsc_class_stats 
 	sp->myfadj = cl->cl_myfadj;
 	sp->vtadj = cl->cl_vtadj;
 
-	sp->cur_time = hfsc_microuptime();
+	sp->cur_time = hfsc_uptime();
 	sp->machclk_freq = HFSC_FREQ;
 
 	sp->qlength = hfsc_class_qlength(cl);