Index: bin/dd/args.c
===================================================================
--- bin/dd/args.c
+++ bin/dd/args.c
@@ -317,6 +317,7 @@
 } clist[] = {
 	{ "ascii",	C_ASCII,	C_EBCDIC,	e2a_POSIX },
 	{ "block",	C_BLOCK,	C_UNBLOCK,	NULL },
+	{ "direct",	C_DIRECT,	0,		NULL },
 	{ "ebcdic",	C_EBCDIC,	C_ASCII,	a2e_POSIX },
 	{ "ibm",	C_EBCDIC,	C_ASCII,	a2ibm_POSIX },
 	{ "lcase",	C_LCASE,	C_UCASE,	NULL },
Index: bin/dd/dd.h
===================================================================
--- bin/dd/dd.h
+++ bin/dd/dd.h
@@ -100,5 +100,6 @@
 #define	C_STATUS	0x08000000
 #define	C_NOXFER	0x10000000
 #define	C_NOINFO	0x20000000
+#define	C_DIRECT	0x40000000
 
 #define	C_PARITY	(C_PAREVEN | C_PARODD | C_PARNONE | C_PARSET)
Index: bin/dd/dd.1
===================================================================
--- bin/dd/dd.1
+++ bin/dd/dd.1
@@ -215,6 +215,8 @@
 Input records longer than the conversion record size are truncated.
 The number of truncated input records, if any, are reported to the standard
 error output at the completion of the copy.
+.It Cm direct
+Open all files O_DIRECT to eliminate or reduce VM cache effects.
 .It Cm ebcdic , ibm , oldebcdic , oldibm
 The same as the
 .Cm block
Index: bin/dd/dd.c
===================================================================
--- bin/dd/dd.c
+++ bin/dd/dd.c
@@ -136,12 +136,15 @@
 	u_int cnt;
 	cap_rights_t rights;
 	unsigned long cmds[] = { FIODTYPE, MTIOCTOP };
+	int oflags = 0;
 
+	if (ddflags & C_DIRECT)
+		oflags |= O_DIRECT;
 	if (in.name == NULL) {
 		in.name = "stdin";
 		in.fd = STDIN_FILENO;
 	} else {
-		in.fd = open(in.name, O_RDONLY, 0);
+		in.fd = open(in.name, O_RDONLY | oflags, 0);
 		if (in.fd == -1)
 			err(1, "%s", in.name);
 	}
@@ -161,16 +164,15 @@
 		out.fd = STDOUT_FILENO;
 		out.name = "stdout";
 	} else {
-#define	OFLAGS \
-    (O_CREAT | (ddflags & (C_SEEK | C_NOTRUNC) ? 0 : O_TRUNC))
-		out.fd = open(out.name, O_RDWR | OFLAGS, DEFFILEMODE);
+		oflags |= O_CREAT | (ddflags & (C_SEEK | C_NOTRUNC) ? 0 : O_TRUNC);
+		out.fd = open(out.name, O_RDWR | oflags, DEFFILEMODE);
 		/*
 		 * May not have read access, so try again with write only.
 		 * Without read we may have a problem if output also does
 		 * not support seeks.
 		 */
 		if (out.fd == -1) {
-			out.fd = open(out.name, O_WRONLY | OFLAGS, DEFFILEMODE);
+			out.fd = open(out.name, O_WRONLY | oflags, DEFFILEMODE);
 			out.flags |= NOREAD;
 			cap_rights_clear(&rights, CAP_READ);
 		}