ruxreset: Add an inline function to reset all the stats in rusage_ext

Use it in proc0_post to reset per-process CPU usage.

Suggested by:	olce
Reviewed by:	olce, kib
Differential Revision:	https://reviews.freebsd.org/D54049

sys/kern/init_main.c

@@ -660,10 +660,7 @@ proc0_post(void *dummy __unused)
 		microuptime(&p->p_stats->p_start);
 		PROC_STATLOCK(p);
 		rufetch(p, &ru);	/* Clears thread stats */
-		p->p_rux.rux_runtime = 0;
-		p->p_rux.rux_uticks = 0;
-		p->p_rux.rux_sticks = 0;
-		p->p_rux.rux_iticks = 0;
+		ruxreset(&p->p_rux);
 		PROC_STATUNLOCK(p);
 		FOREACH_THREAD_IN_PROC(p, td) {
 			td->td_runtime = 0;

sys/sys/proc.h

@@ -1326,6 +1326,18 @@ td_get_sched(struct thread *td)
 	return ((struct td_sched *)&td[1]);
 }
 
+static __inline void
+ruxreset(struct rusage_ext *rux)
+{
+	rux->rux_runtime = 0;
+	rux->rux_uticks = 0;
+	rux->rux_sticks = 0;
+	rux->rux_iticks = 0;
+	rux->rux_uu = 0;
+	rux->rux_su = 0;
+	rux->rux_tu = 0;
+}
+
 #define	PROC_ID_PID	0
 #define	PROC_ID_GROUP	1
 #define	PROC_ID_SESSION	2