The tunable parameter for the scheduler quantum was inverted.

Higher numbers led to smaller quanta.
In discussion with BDE, change this parameter to be in uSecs
to make it machine independent,
and limit it to non zero multiples of 'tick' (rounding down).
Also make the variabel globally available so that the present function that
returns its value (used for posix scheduling I believe) can go away.

Submitted by: Bruce Evans <bde@freebsd.org>

2 files changed, 25 insertions, 31 deletions

diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index 8473adee..892f8bb 100644
--- a/sys/kern/kern_synch.c
+++ b/sys/kern/kern_synch.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)kern_synch.c	8.9 (Berkeley) 5/19/95
- * $Id: kern_synch.c,v 1.73 1999/02/22 16:57:47 bde Exp $
+ * $Id: kern_synch.c,v 1.74 1999/02/28 10:53:29 bde Exp $
  */
 
 #include "opt_ktrace.h"
@@ -64,43 +64,37 @@
 
 static void rqinit __P((void *));
 SYSINIT(runqueue, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, rqinit, NULL)
+static void sched_setup __P((void *dummy));
+SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL)
 
-u_char	curpriority;		/* usrpri of curproc */
+u_char	curpriority;
 int	hogticks;
-int	lbolt;			/* once a second sleep address */
+int	lbolt;
+int	sched_quantum;		/* Roundrobin scheduling quantum in ticks. */
 
 static void	endtsleep __P((void *));
 static void	roundrobin __P((void *arg));
 static void	schedcpu __P((void *arg));
 static void	updatepri __P((struct proc *p));
 
-#define MAXIMUM_SCHEDULE_QUANTUM	(1000000) /* arbitrary limit */
-#ifndef DEFAULT_SCHEDULE_QUANTUM
-#define DEFAULT_SCHEDULE_QUANTUM 10
-#endif
-static int quantum = DEFAULT_SCHEDULE_QUANTUM; /* default value */
-
 static int
 sysctl_kern_quantum SYSCTL_HANDLER_ARGS
 {
-	int error;
-	int new_val = quantum;
+	int error, new_val;
 
-	new_val = quantum;
+	new_val = sched_quantum * tick;
 	error = sysctl_handle_int(oidp, &new_val, 0, req);
-	if (error == 0) {
-		if ((new_val > 0) && (new_val < MAXIMUM_SCHEDULE_QUANTUM)) {
-			quantum = new_val;
-		} else {
-			error = EINVAL;
-		}
-	}
-	hogticks = 2 * (hz / quantum);
-	return (error);
+        if (error != 0 || req->newptr == NULL)
+		return (error);
+	if (new_val < tick)
+		return (EINVAL);
+	sched_quantum = new_val / tick;
+	hogticks = 2 * sched_quantum;
+	return (0);
 }
 
 SYSCTL_PROC(_kern, OID_AUTO, quantum, CTLTYPE_INT|CTLFLAG_RW,
-	0, sizeof quantum, sysctl_kern_quantum, "I", "");
+	0, sizeof sched_quantum, sysctl_kern_quantum, "I", "");
 
 /* maybe_resched: Decide if you need to reschedule or not
  * taking the priorities and schedulers into account.
@@ -126,10 +120,10 @@ static void maybe_resched(struct proc *chk)
 	}
 }
 
-#define ROUNDROBIN_INTERVAL (hz / quantum)
-int roundrobin_interval(void)
+int 
+roundrobin_interval(void)
 {
-	return ROUNDROBIN_INTERVAL;
+	return (sched_quantum);
 }
 
 /*
@@ -152,7 +146,7 @@ roundrobin(arg)
  		need_resched();
 #endif
 
- 	timeout(roundrobin, NULL, ROUNDROBIN_INTERVAL);
+ 	timeout(roundrobin, NULL, sched_quantum);
 }
 
 /*
@@ -358,11 +352,12 @@ static TAILQ_HEAD(slpquehead, proc) slpque[TABLESIZE];
 int safepri;
 
 void
-sleepinit()
+sleepinit(void)
 {
 	int i;
 
-	hogticks = 2 * (hz / quantum);
+	sched_quantum = hz/10;
+	hogticks = 2 * sched_quantum;
 	for (i = 0; i < TABLESIZE; i++)
 		TAILQ_INIT(&slpque[i]);
 }
@@ -915,7 +910,6 @@ resetpriority(p)
 }
 
 /* ARGSUSED */
-static void sched_setup __P((void *dummy));
 static void
 sched_setup(dummy)
 	void *dummy;
@@ -924,5 +918,4 @@ sched_setup(dummy)
 	roundrobin(NULL);
 	schedcpu(NULL);
 }
-SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL)
 
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 53eef6d..1d0a9b7 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)proc.h	8.15 (Berkeley) 5/19/95
- * $Id: proc.h,v 1.71 1999/02/25 14:28:46 newton Exp $
+ * $Id: proc.h,v 1.72 1999/02/28 10:53:29 bde Exp $
  */
 
 #ifndef _SYS_PROC_H_
@@ -329,6 +329,7 @@ extern struct proc proc0;		/* Process slot for swapper. */
 extern int hogticks;			/* Limit on kernel cpu hogs. */
 extern int nprocs, maxproc;		/* Current and max number of procs. */
 extern int maxprocperuid;		/* Max procs per uid. */
+extern int sched_quantum;		/* Scheduling quantum in ticks */
 extern int switchticks;			/* `ticks' at last context switch. */
 extern struct timeval switchtime;	/* Uptime at last context switch */