Index: include/unistd.h
===================================================================
--- include/unistd.h
+++ include/unistd.h
@@ -571,6 +571,7 @@
 void	*setmode(const char *);
 int	 setpgrp(pid_t, pid_t);			/* obsoleted by setpgid() */
 void	 setproctitle(const char *_fmt, ...) __printf0like(1, 2);
+void	 setproctitle_fast(const char *_fmt, ...) __printf0like(1, 2);
 int	 setresgid(gid_t, gid_t, gid_t);
 int	 setresuid(uid_t, uid_t, uid_t);
 int	 setrgid(gid_t);
Index: lib/libc/gen/setproctitle.3
===================================================================
--- lib/libc/gen/setproctitle.3
+++ lib/libc/gen/setproctitle.3
@@ -31,12 +31,18 @@
 .In unistd.h
 .Ft void
 .Fn setproctitle "const char *fmt" "..."
+.Ft void
+.Fn setproctitle_fast "const char *fmt" "..."
 .Sh DESCRIPTION
 The
 .Fn setproctitle
 library routine sets the process title that appears on the
 .Xr ps 1
-command.
+command.  The
+.Fn setproctitle_fast
+variant is optimized for high frequency updates, but may make the
+.Xr ps 1
+command slightly slower.
 .Pp
 The title is set from the executable's name, followed by the
 result of a
@@ -96,6 +102,10 @@
 function
 first appeared in
 .Fx 2.2 .
+The
+.Fn setproctitle_fast
+function first appeared in
+.Fx 12 .
 Other operating systems have
 similar functions.
 .Sh AUTHORS
Index: lib/libc/gen/setproctitle.c
===================================================================
--- lib/libc/gen/setproctitle.c
+++ lib/libc/gen/setproctitle.c
@@ -55,8 +55,8 @@
 
 #define SPT_BUFSIZE 2048	/* from other parts of sendmail */
 
-void
-setproctitle(const char *fmt, ...)
+static inline char *
+setproctitle_internal(const char *fmt, va_list ap)
 {
 	static struct ps_strings *ps_strings;
 	static char *buf = NULL;
@@ -67,27 +67,23 @@
 	char **nargvp;
 	int nargc;
 	int i;
-	va_list ap;
 	size_t len;
 	unsigned long ul_ps_strings;
-	int oid[4];
 
 	if (buf == NULL) {
 		buf = malloc(SPT_BUFSIZE);
 		if (buf == NULL) 
-			return;
+			return NULL;
 		nargv[0] = buf;
 	}
 
 	if (obuf == NULL ) {
 		obuf = malloc(SPT_BUFSIZE);
 		if (obuf == NULL)
-			return;
+			return NULL;
 		*obuf = '\0';
 	}
 
-	va_start(ap, fmt);
-
 	if (fmt) {
 		buf[SPT_BUFSIZE - 1] = '\0';
 
@@ -114,22 +110,13 @@
 		kbuf = obuf;
 	} else
 		/* Nothing to restore */
-		return;
-
-	va_end(ap);
-
-	/* Set the title into the kernel cached command line */
-	oid[0] = CTL_KERN;
-	oid[1] = KERN_PROC;
-	oid[2] = KERN_PROC_ARGS;
-	oid[3] = getpid();
-	sysctl(oid, 4, 0, 0, kbuf, strlen(kbuf) + 1);
+		return NULL;
 
 	if (ps_strings == NULL) {
 		len = sizeof(ul_ps_strings);
 		if (sysctlbyname("kern.ps_strings", &ul_ps_strings, &len, NULL,
 		    0) == -1)
-			return;
+			return NULL;
 		ps_strings = (struct ps_strings *)ul_ps_strings;
 	}
 
@@ -138,7 +125,7 @@
 	 * Should not happen.
 	 */
 	if (ps_strings->ps_argvstr == NULL)
-		return;
+		return NULL;
 
 	/* style #3 */
 	if (oargc == -1) {
@@ -167,4 +154,55 @@
 	}
 	ps_strings->ps_nargvstr = nargc;
 	ps_strings->ps_argvstr = nargvp;
+
+	return nargvp[0];
+}
+
+static int fast_update = 0;
+
+void
+setproctitle_fast(const char *fmt, ...)
+{
+	va_list ap;
+	char *buf;
+	int oid[4];
+
+	va_start(ap, fmt);
+	buf = setproctitle_internal(fmt, ap);
+	va_end(ap);
+
+	if (!buf)
+		return;
+
+	if (!fast_update) {
+		/* Tell the kernel to start looking in user-space */
+		oid[0] = CTL_KERN;
+		oid[1] = KERN_PROC;
+		oid[2] = KERN_PROC_ARGS;
+		oid[3] = getpid();
+		sysctl(oid, 4, 0, 0, "", 0);
+		fast_update = 1;
+	}
+}
+
+void
+setproctitle(const char *fmt, ...)
+{
+	va_list ap;
+	char *buf;
+	int oid[4];
+
+	va_start(ap, fmt);
+	buf = setproctitle_internal(fmt, ap);
+	va_end(ap);
+
+	if (buf) {
+		/* Set the title into the kernel cached command line */
+		oid[0] = CTL_KERN;
+		oid[1] = KERN_PROC;
+		oid[2] = KERN_PROC_ARGS;
+		oid[3] = getpid();
+		sysctl(oid, 4, 0, 0, buf, strlen(buf) + 1);
+		fast_update = 0;
+	}
 }
Index: sys/kern/kern_proc.c
===================================================================
--- sys/kern/kern_proc.c
+++ sys/kern/kern_proc.c
@@ -1988,11 +1988,20 @@
 
 	if (req->newlen > ps_arg_cache_limit - sizeof(struct pargs))
 		return (ENOMEM);
-	newpa = pargs_alloc(req->newlen);
-	error = SYSCTL_IN(req, newpa->ar_args, req->newlen);
-	if (error != 0) {
-		pargs_free(newpa);
-		return (error);
+
+	if (req->newlen == 0) {
+		/*
+		 * Clear the argument pointer, so that we'll fetch arguments
+		 * with proc_getargv() until further notice.
+		 */
+		newpa = NULL;
+	} else {
+		newpa = pargs_alloc(req->newlen);
+		error = SYSCTL_IN(req, newpa->ar_args, req->newlen);
+		if (error != 0) {
+			pargs_free(newpa);
+			return (error);
+		}
 	}
 	PROC_LOCK(p);
 	pa = p->p_args;
Index: usr.bin/top/machine.c
===================================================================
--- usr.bin/top/machine.c
+++ usr.bin/top/machine.c
@@ -950,7 +950,6 @@
 		}
 	} else {
 		if (pp->ki_flag & P_SYSTEM ||
-		    pp->ki_args == NULL ||
 		    (args = kvm_getargv(kd, pp, cmdlen)) == NULL ||
 		    !(*args)) {
 			if (ps.thread && pp->ki_flag & P_HADTHREADS &&