Improved scheduling in uiomove(), etc. resched_wanted() is true too

often for it to be a good criterion for switching kernel cpu hogs --
it is true after most wakeups.  Use the criterion "has been running
for >= 2 quanta" instead.

3 files changed, 15 insertions, 8 deletions

diff --git a/sys/kern/kern_subr.c b/sys/kern/kern_subr.c
index d8e1f08..7f14488 100644
--- a/sys/kern/kern_subr.c
+++ b/sys/kern/kern_subr.c
@@ -36,11 +36,12 @@
  * SUCH DAMAGE.
  *
  *	@(#)kern_subr.c	8.3 (Berkeley) 1/21/94
- * $Id: kern_subr.c,v 1.24 1999/01/10 01:58:24 eivind Exp $
+ * $Id: kern_subr.c,v 1.25 1999/02/02 12:11:01 bde Exp $
  */
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/kernel.h>
 #include <sys/proc.h>
 #include <sys/malloc.h>
 #include <sys/lock.h>
@@ -52,8 +53,6 @@
 #include <vm/vm_page.h>
 #include <vm/vm_map.h>
 
-#include <machine/cpu.h>
-
 static void	uio_yield __P((void));
 
 int
@@ -86,7 +85,7 @@ uiomove(cp, n, uio)
 
 		case UIO_USERSPACE:
 		case UIO_USERISPACE:
-			if (resched_wanted())
+			if (ticks - switchticks >= hogticks)
 				uio_yield();
 			if (uio->uio_rw == UIO_READ)
 				error = copyout(cp, iov->iov_base, cnt);
@@ -146,7 +145,7 @@ uiomoveco(cp, n, uio, obj)
 
 		case UIO_USERSPACE:
 		case UIO_USERISPACE:
-			if (resched_wanted())
+			if (ticks - switchticks >= hogticks)
 				uio_yield();
 			if (uio->uio_rw == UIO_READ) {
 				if (vfs_ioopt && ((cnt & PAGE_MASK) == 0) &&
@@ -223,7 +222,7 @@ uioread(n, uio, obj, nread)
 
 			cnt &= ~PAGE_MASK;
 
-			if (resched_wanted())
+			if (ticks - switchticks >= hogticks)
 				uio_yield();
 			error = vm_uiomove(&curproc->p_vmspace->vm_map, obj,
 						uio->uio_offset, cnt,
@@ -408,6 +407,7 @@ uio_yield()
 	int s;
 
 	p = curproc;
+	p->p_priority = p->p_usrpri;
 	s = splhigh();
 	setrunqueue(p);
 	p->p_stats->p_ru.ru_nivcsw++;
diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index f8baf85..bea45f7 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 1.71 1999/01/08 17:31:10 eivind Exp $
+ * $Id: kern_synch.c,v 1.72 1999/01/10 01:58:24 eivind Exp $
  */
 
 #include "opt_ktrace.h"
@@ -66,6 +66,7 @@ static void rqinit __P((void *));
 SYSINIT(runqueue, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, rqinit, NULL)
 
 u_char	curpriority;		/* usrpri of curproc */
+int	hogticks;
 int	lbolt;			/* once a second sleep address */
 
 static void	endtsleep __P((void *));
@@ -94,6 +95,7 @@ sysctl_kern_quantum SYSCTL_HANDLER_ARGS
 			error = EINVAL;
 		}
 	}
+	hogticks = 2 * (hz / quantum);
 	return (error);
 }
 
@@ -360,6 +362,7 @@ sleepinit()
 {
 	int i;
 
+	hogticks = 2 * (hz / quantum);
 	for (i = 0; i < TABLESIZE; i++)
 		TAILQ_INIT(&slpque[i]);
 }
@@ -828,6 +831,8 @@ mi_switch()
 		p->p_switchtime = switchtime;
 	else
 		microuptime(&p->p_switchtime);
+	switchticks = ticks;
+
 	splx(x);
 }
 
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index a13ce76..bc2f771 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 1.68 1999/02/01 13:23:18 newton Exp $
+ * $Id: proc.h,v 1.69 1999/02/03 08:21:44 bde Exp $
  */
 
 #ifndef _SYS_PROC_H_
@@ -326,8 +326,10 @@ extern u_long pgrphash;
 
 extern struct proc *curproc;		/* Current running proc. */
 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 switchticks;			/* `ticks' at last context switch. */
 extern struct timeval switchtime;	/* Uptime at last context switch */
 
 LIST_HEAD(proclist, proc);