Note: this is just a simple port from Martin Schulze's Linux syslogd to
FreeBSD 5.2.1.  All the credit goes to him, and flames to me ;-)

Note: I didn't port the support for buffered pipes.
--- syslog.conf.5.orig	Thu Feb 13 02:08:56 2003
+++ syslog.conf.5	Sun May 30 09:04:23 2004
@@ -318,6 +318,16 @@
 .It
 A pathname (beginning with a leading slash).
 Selected messages are appended to the file.
+.Pp
+FreeBSD by default syncs after writing a message from the kernel;
+non-kernel messages are never sync'ed.
+You may prefix each entry with the minus ``-'' sign to omit
+syncing the file after every logging from the kernel.
+Note that you might lose information if the system
+crashes right behind a write attempt.
+Nevertheless this might give you back some performance,
+especially if you log from the kernel
+in a very verbose manner.
 .It
 A hostname (preceded by an at
 .Pq Dq @
--- syslogd.c.orig	Sun Nov 16 23:51:06 2003
+++ syslogd.c	Sun May 30 09:08:24 2004
@@ -184,6 +184,7 @@
 	int	f_prevlen;			/* length of f_prevline */
 	int	f_prevcount;			/* repetition cnt of prevline */
 	u_int	f_repeatcount;			/* number of "repeated" msgs */
+	int	f_flags;			/* store file-specific sync flag */
 };
 
 /*
@@ -738,7 +739,7 @@
 {
 	int pri, flags;
 
-	flags = ISKERNEL | SYNC_FILE | ADDDATE;	/* fsync after write */
+	flags = ISKERNEL | ADDDATE;
 	pri = DEFSPRI;
 	if (*p == '<') {
 		pri = 0;
@@ -1130,7 +1131,7 @@
 			f->f_type = F_UNUSED;
 			errno = e;
 			logerror(f->f_un.f_fname);
-		} else if (flags & SYNC_FILE)
+		} else if (flags && f->f_flags & SYNC_FILE) /* never sync non-kernel files */
 			(void)fsync(f->f_file);
 		break;
 
@@ -1611,7 +1612,7 @@
 cfline(const char *line, struct filed *f, const char *prog, const char *host)
 {
 	struct addrinfo hints, *res;
-	int error, i, pri;
+	int error, i, pri, syncfile;
 	const char *p, *q;
 	char *bp;
 	char buf[MAXLINE], ebuf[100];
@@ -1755,6 +1756,12 @@
 	while (*p == '\t' || *p == ' ')
 		p++;
 
+	if (*p == '-') {
+		syncfile = 0;
+		p++;
+	} else
+		syncfile = 1;
+
 	switch (*p) {
 	case '@':
 		(void)strlcpy(f->f_un.f_forw.f_hname, ++p,
@@ -1778,6 +1785,8 @@
 			logerror(p);
 			break;
 		}
+		if (syncfile)
+			f->f_flags |= SYNC_FILE;
 		if (isatty(f->f_file)) {
 			if (strcmp(p, ctty) == 0)
 				f->f_type = F_CONSOLE;