diff mbox series

[net-next,v3,3/3] selftests: add MSG_ZEROCOPY msg_control notification test

Message ID 20240510155900.1825946-4-zijianzhang@bytedance.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series net: A lightweight zero-copy notification | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next, async
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 8 this patch: 8
netdev/build_tools success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers warning 4 maintainers not CCed: pabeni@redhat.com kuba@kernel.org linux-kselftest@vger.kernel.org shuah@kernel.org
netdev/build_clang success Errors and warnings before: 8 this patch: 8
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success net selftest script(s) already in Makefile
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 8 this patch: 8
netdev/checkpatch warning CHECK: Alignment should match open parenthesis CHECK: braces {} should be used on all arms of this statement WARNING: line length of 86 exceeds 80 columns WARNING: line length of 90 exceeds 80 columns WARNING: line length of 93 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Zijian Zhang May 10, 2024, 3:59 p.m. UTC 
From: Zijian Zhang <zijianzhang@bytedance.com>

We update selftests/net/msg_zerocopy.c to accommodate the new mechanism.

Test result from selftests/net/msg_zerocopy.c,
cfg_notification_limit = 1, in this case MSG_ZEROCOPY approximately
aligns with the semantics of MSG_ZEROCOPY_UARG. In this case, the new
flag has around 13% cpu savings in TCP and 18% cpu savings in UDP.
+---------------------+---------+---------+---------+---------+
| Test Type / Protocol| TCP v4  | TCP v6  | UDP v4  | UDP v6  |
+---------------------+---------+---------+---------+---------+
| ZCopy (MB)          | 5147    | 4885    | 7489    | 7854    |
+---------------------+---------+---------+---------+---------+
| New ZCopy (MB)      | 5859    | 5505    | 9053    | 9236    |
+---------------------+---------+---------+---------+---------+
| New ZCopy / ZCopy   | 113.83% | 112.69% | 120.88% | 117.59% |
+---------------------+---------+---------+---------+---------+

cfg_notification_limit = 32, it means less poll + recvmsg overhead,
the new mechanism performs 8% better in TCP. For UDP, no obvious
performance gain is observed and sometimes may lead to degradation.
Thus, if users don't need to retrieve the notification ASAP in UDP,
the original mechanism is preferred.
+---------------------+---------+---------+---------+---------+
| Test Type / Protocol| TCP v4  | TCP v6  | UDP v4  | UDP v6  |
+---------------------+---------+---------+---------+---------+
| ZCopy (MB)          | 6272    | 6138    | 12138   | 10055   |
+---------------------+---------+---------+---------+---------+
| New ZCopy (MB)      | 6774    | 6620    | 11504   | 10355   |
+---------------------+---------+---------+---------+---------+
| New ZCopy / ZCopy   | 108.00% | 107.85% | 94.78%  | 102.98% |
+---------------------+---------+---------+---------+---------+

Signed-off-by: Zijian Zhang <zijianzhang@bytedance.com>
Signed-off-by: Xiaochun Lu <xiaochun.lu@bytedance.com>
---
 tools/testing/selftests/net/msg_zerocopy.c  | 103 ++++++++++++++++++--
 tools/testing/selftests/net/msg_zerocopy.sh |   1 +
 2 files changed, 97 insertions(+), 7 deletions(-)

Comments

Willem de Bruijn May 13, 2024, 1:02 a.m. UTC | #1 
zijianzhang@ wrote:
> From: Zijian Zhang <zijianzhang@bytedance.com>
> 
> We update selftests/net/msg_zerocopy.c to accommodate the new mechanism.
> 
> Test result from selftests/net/msg_zerocopy.c,
> cfg_notification_limit = 1, in this case MSG_ZEROCOPY approximately
> aligns with the semantics of MSG_ZEROCOPY_UARG. In this case, the new
> flag has around 13% cpu savings in TCP and 18% cpu savings in UDP.
> +---------------------+---------+---------+---------+---------+
> | Test Type / Protocol| TCP v4  | TCP v6  | UDP v4  | UDP v6  |
> +---------------------+---------+---------+---------+---------+
> | ZCopy (MB)          | 5147    | 4885    | 7489    | 7854    |
> +---------------------+---------+---------+---------+---------+
> | New ZCopy (MB)      | 5859    | 5505    | 9053    | 9236    |
> +---------------------+---------+---------+---------+---------+
> | New ZCopy / ZCopy   | 113.83% | 112.69% | 120.88% | 117.59% |
> +---------------------+---------+---------+---------+---------+
> 
> cfg_notification_limit = 32, it means less poll + recvmsg overhead,
> the new mechanism performs 8% better in TCP. For UDP, no obvious
> performance gain is observed and sometimes may lead to degradation.
> Thus, if users don't need to retrieve the notification ASAP in UDP,
> the original mechanism is preferred.
> +---------------------+---------+---------+---------+---------+
> | Test Type / Protocol| TCP v4  | TCP v6  | UDP v4  | UDP v6  |
> +---------------------+---------+---------+---------+---------+
> | ZCopy (MB)          | 6272    | 6138    | 12138   | 10055   |
> +---------------------+---------+---------+---------+---------+
> | New ZCopy (MB)      | 6774    | 6620    | 11504   | 10355   |
> +---------------------+---------+---------+---------+---------+
> | New ZCopy / ZCopy   | 108.00% | 107.85% | 94.78%  | 102.98% |
> +---------------------+---------+---------+---------+---------+
> 
> Signed-off-by: Zijian Zhang <zijianzhang@bytedance.com>
> Signed-off-by: Xiaochun Lu <xiaochun.lu@bytedance.com>
> ---
>  tools/testing/selftests/net/msg_zerocopy.c  | 103 ++++++++++++++++++--
>  tools/testing/selftests/net/msg_zerocopy.sh |   1 +
>  2 files changed, 97 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/testing/selftests/net/msg_zerocopy.c b/tools/testing/selftests/net/msg_zerocopy.c
> index ba6c257f689c..48750a7a162c 100644
> --- a/tools/testing/selftests/net/msg_zerocopy.c
> +++ b/tools/testing/selftests/net/msg_zerocopy.c
> @@ -1,3 +1,4 @@
> +// SPDX-License-Identifier: GPL-2.0
>  /* Evaluate MSG_ZEROCOPY
>   *
>   * Send traffic between two processes over one of the supported
> @@ -66,6 +67,10 @@
>  #define SO_ZEROCOPY	60
>  #endif
>  
> +#ifndef SCM_ZC_NOTIFICATION
> +#define SCM_ZC_NOTIFICATION	78
> +#endif
> +
>  #ifndef SO_EE_CODE_ZEROCOPY_COPIED
>  #define SO_EE_CODE_ZEROCOPY_COPIED	1
>  #endif
> @@ -74,6 +79,13 @@
>  #define MSG_ZEROCOPY	0x4000000
>  #endif
>  
> +#define ZC_MSGERR_NOTIFICATION 1
> +#define ZC_MSGCTL_NOTIFICATION 2

Please define an enum

And consider less truncated, more descriptive, names. E.g.,

   MSG_ZEROCOPY_NOTIFY_ERRQUEUE
   MSG_ZEROCOPY_NOTIFY_SENDMSG

> +
> +#define SOCK_ZC_INFO_NUM 8
> +
> +#define INVALID_ZEROCOPY_VAL 2
> +
>  static int  cfg_cork;
>  static bool cfg_cork_mixed;
>  static int  cfg_cpu		= -1;		/* default: pin to last cpu */
> @@ -86,13 +98,16 @@ static int  cfg_runtime_ms	= 4200;
>  static int  cfg_verbose;
>  static int  cfg_waittime_ms	= 500;
>  static int  cfg_notification_limit = 32;
> -static bool cfg_zerocopy;
> +static int  cfg_zerocopy;           /* Either 1 or 2, mode for SO_ZEROCOPY */
>  
>  static socklen_t cfg_alen;
>  static struct sockaddr_storage cfg_dst_addr;
>  static struct sockaddr_storage cfg_src_addr;
>  
>  static char payload[IP_MAXPACKET];
> +static struct zc_info_elem zc_info[SOCK_ZC_INFO_NUM];
> +static char zc_ckbuf[CMSG_SPACE(sizeof(void *))];
> +static struct zc_info_elem *zc_info_ptr = zc_info;
>  static long packets, bytes, completions, expected_completions;
>  static int  zerocopied = -1;
>  static uint32_t next_completion;
> @@ -170,6 +185,26 @@ static int do_accept(int fd)
>  	return fd;
>  }
>  
> +static void add_zcopy_info(struct msghdr *msg)
> +{
> +	int i;
> +	struct cmsghdr *cm;
> +
> +	if (!msg->msg_control)
> +		error(1, errno, "NULL user arg");
> +	cm = (void *)msg->msg_control;
> +	/* Although only the address of the array will be written into the
> +	 * zc_ckbuf, we assign cmsg_len to CMSG_LEN(sizeof(zc_info)) to specify
> +	 * the length of the array.
> +	 */
> +	cm->cmsg_len = CMSG_LEN(sizeof(zc_info));
> +	cm->cmsg_level = SOL_SOCKET;
> +	cm->cmsg_type = SCM_ZC_NOTIFICATION;
> +	memcpy(CMSG_DATA(cm), &zc_info_ptr, sizeof(zc_info_ptr));
> +	for (i = 0; i < SOCK_ZC_INFO_NUM; i++)
> +		zc_info[i].zerocopy = INVALID_ZEROCOPY_VAL;
> +}
> +
>  static void add_zcopy_cookie(struct msghdr *msg, uint32_t cookie)
>  {
>  	struct cmsghdr *cm;
> @@ -183,7 +218,7 @@ static void add_zcopy_cookie(struct msghdr *msg, uint32_t cookie)
>  	memcpy(CMSG_DATA(cm), &cookie, sizeof(cookie));
>  }
>  
> -static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain)
> +static bool do_sendmsg(int fd, struct msghdr *msg, int do_zerocopy, int domain)
>  {
>  	int ret, len, i, flags;
>  	static uint32_t cookie;
> @@ -201,6 +236,15 @@ static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain)
>  			msg->msg_controllen = CMSG_SPACE(sizeof(cookie));
>  			msg->msg_control = (struct cmsghdr *)ckbuf;
>  			add_zcopy_cookie(msg, ++cookie);
> +		} else if (do_zerocopy == ZC_MSGCTL_NOTIFICATION) {
> +			memset(&msg->msg_control, 0, sizeof(msg->msg_control));
> +			/* Although only the address of the array will be written into the
> +			 * zc_ckbuf, msg_controllen must be larger or equal than any cmsg_len
> +			 * in it. Otherwise, we will get -EINVAL.
> +			 */
> +			msg->msg_controllen = CMSG_SPACE(sizeof(zc_info));
> +			msg->msg_control = (struct cmsghdr *)zc_ckbuf;
> +			add_zcopy_info(msg);
>  		}
>  	}
>  
> @@ -219,7 +263,7 @@ static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain)
>  		if (do_zerocopy && ret)
>  			expected_completions++;
>  	}
> -	if (do_zerocopy && domain == PF_RDS) {
> +	if (msg->msg_control) {
>  		msg->msg_control = NULL;
>  		msg->msg_controllen = 0;
>  	}
> @@ -393,6 +437,42 @@ static bool do_recvmsg_completion(int fd)
>  	return ret;
>  }
>  
> +static void do_recv_completions2(void)
> +{
> +	int i;
> +	__u32 hi, lo, range;
> +	__u8 zerocopy;
> +
> +	for (i = 0; zc_info[i].zerocopy != INVALID_ZEROCOPY_VAL; i++) {
> +		struct zc_info_elem elem = zc_info[i];
> +
> +		hi = elem.hi;
> +		lo = elem.lo;
> +		zerocopy = elem.zerocopy;
> +		range = hi - lo + 1;
> +
> +		if (cfg_verbose && lo != next_completion)
> +			fprintf(stderr, "gap: %u..%u does not append to %u\n",
> +				lo, hi, next_completion);
> +		next_completion = hi + 1;
> +
> +		if (zerocopied == -1)
> +			zerocopied = zerocopy;
> +		else if (zerocopied != zerocopy) {
> +			fprintf(stderr, "serr: inconsistent\n");
> +			zerocopied = zerocopy;
> +		}
> +
> +		completions += range;
> +
> +		if (cfg_verbose >= 2)
> +			fprintf(stderr, "completed: %u (h=%u l=%u)\n",
> +				range, hi, lo);
> +	}
> +
> +	sendmsg_counter -= i;
> +}
> +
>  static bool do_recv_completion(int fd, int domain)
>  {
>  	struct sock_extended_err *serr;
> @@ -554,11 +634,15 @@ static void do_tx(int domain, int type, int protocol)
>  		else
>  			do_sendmsg(fd, &msg, cfg_zerocopy, domain);
>  
> -		if (cfg_zerocopy && sendmsg_counter >= cfg_notification_limit)
> +		if (cfg_zerocopy == ZC_MSGERR_NOTIFICATION &&
> +			sendmsg_counter >= cfg_notification_limit)
>  			do_recv_completions(fd, domain);
>  
> +		if (cfg_zerocopy == ZC_MSGCTL_NOTIFICATION)
> +			do_recv_completions2();
> +
>  		while (!do_poll(fd, POLLOUT)) {
> -			if (cfg_zerocopy)
> +			if (cfg_zerocopy == ZC_MSGERR_NOTIFICATION)
>  				do_recv_completions(fd, domain);
>  		}
>  
> @@ -716,7 +800,7 @@ static void parse_opts(int argc, char **argv)
>  
>  	cfg_payload_len = max_payload_len;
>  
> -	while ((c = getopt(argc, argv, "46c:C:D:i:l:mp:rs:S:t:vz")) != -1) {
> +	while ((c = getopt(argc, argv, "46c:C:D:i:l:mnp:rs:S:t:vz")) != -1) {
>  		switch (c) {
>  		case '4':
>  			if (cfg_family != PF_UNSPEC)
> @@ -750,6 +834,9 @@ static void parse_opts(int argc, char **argv)
>  		case 'm':
>  			cfg_cork_mixed = true;
>  			break;
> +		case 'n':
> +			cfg_zerocopy = ZC_MSGCTL_NOTIFICATION;
> +			break;
>  		case 'p':
>  			cfg_port = strtoul(optarg, NULL, 0);
>  			break;
> @@ -769,7 +856,7 @@ static void parse_opts(int argc, char **argv)
>  			cfg_verbose++;
>  			break;
>  		case 'z':
> -			cfg_zerocopy = true;
> +			cfg_zerocopy = ZC_MSGERR_NOTIFICATION;
>  			break;
>  		}
>  	}
> @@ -780,6 +867,8 @@ static void parse_opts(int argc, char **argv)
>  			error(1, 0, "-D <server addr> required for PF_RDS\n");
>  		if (!cfg_rx && !saddr)
>  			error(1, 0, "-S <client addr> required for PF_RDS\n");
> +		if (cfg_zerocopy == ZC_MSGCTL_NOTIFICATION)
> +			error(1, 0, "PF_RDS does not support ZC_MSGCTL_NOTIFICATION");
>  	}
>  	setup_sockaddr(cfg_family, daddr, &cfg_dst_addr);
>  	setup_sockaddr(cfg_family, saddr, &cfg_src_addr);
> diff --git a/tools/testing/selftests/net/msg_zerocopy.sh b/tools/testing/selftests/net/msg_zerocopy.sh
> index 89c22f5320e0..022a6936d86f 100755
> --- a/tools/testing/selftests/net/msg_zerocopy.sh
> +++ b/tools/testing/selftests/net/msg_zerocopy.sh
> @@ -118,4 +118,5 @@ do_test() {
>  
>  do_test "${EXTRA_ARGS}"
>  do_test "-z ${EXTRA_ARGS}"
> +do_test "-n ${EXTRA_ARGS}"
>  echo ok
> -- 
> 2.20.1
>
diff mbox series

Patch

diff --git a/tools/testing/selftests/net/msg_zerocopy.c b/tools/testing/selftests/net/msg_zerocopy.c
index ba6c257f689c..48750a7a162c 100644
--- a/tools/testing/selftests/net/msg_zerocopy.c
+++ b/tools/testing/selftests/net/msg_zerocopy.c
@@ -1,3 +1,4 @@ 
+// SPDX-License-Identifier: GPL-2.0
 /* Evaluate MSG_ZEROCOPY
  *
  * Send traffic between two processes over one of the supported
@@ -66,6 +67,10 @@ 
 #define SO_ZEROCOPY	60
 #endif
 
+#ifndef SCM_ZC_NOTIFICATION
+#define SCM_ZC_NOTIFICATION	78
+#endif
+
 #ifndef SO_EE_CODE_ZEROCOPY_COPIED
 #define SO_EE_CODE_ZEROCOPY_COPIED	1
 #endif
@@ -74,6 +79,13 @@ 
 #define MSG_ZEROCOPY	0x4000000
 #endif
 
+#define ZC_MSGERR_NOTIFICATION 1
+#define ZC_MSGCTL_NOTIFICATION 2
+
+#define SOCK_ZC_INFO_NUM 8
+
+#define INVALID_ZEROCOPY_VAL 2
+
 static int  cfg_cork;
 static bool cfg_cork_mixed;
 static int  cfg_cpu		= -1;		/* default: pin to last cpu */
@@ -86,13 +98,16 @@  static int  cfg_runtime_ms	= 4200;
 static int  cfg_verbose;
 static int  cfg_waittime_ms	= 500;
 static int  cfg_notification_limit = 32;
-static bool cfg_zerocopy;
+static int  cfg_zerocopy;           /* Either 1 or 2, mode for SO_ZEROCOPY */
 
 static socklen_t cfg_alen;
 static struct sockaddr_storage cfg_dst_addr;
 static struct sockaddr_storage cfg_src_addr;
 
 static char payload[IP_MAXPACKET];
+static struct zc_info_elem zc_info[SOCK_ZC_INFO_NUM];
+static char zc_ckbuf[CMSG_SPACE(sizeof(void *))];
+static struct zc_info_elem *zc_info_ptr = zc_info;
 static long packets, bytes, completions, expected_completions;
 static int  zerocopied = -1;
 static uint32_t next_completion;
@@ -170,6 +185,26 @@  static int do_accept(int fd)
 	return fd;
 }
 
+static void add_zcopy_info(struct msghdr *msg)
+{
+	int i;
+	struct cmsghdr *cm;
+
+	if (!msg->msg_control)
+		error(1, errno, "NULL user arg");
+	cm = (void *)msg->msg_control;
+	/* Although only the address of the array will be written into the
+	 * zc_ckbuf, we assign cmsg_len to CMSG_LEN(sizeof(zc_info)) to specify
+	 * the length of the array.
+	 */
+	cm->cmsg_len = CMSG_LEN(sizeof(zc_info));
+	cm->cmsg_level = SOL_SOCKET;
+	cm->cmsg_type = SCM_ZC_NOTIFICATION;
+	memcpy(CMSG_DATA(cm), &zc_info_ptr, sizeof(zc_info_ptr));
+	for (i = 0; i < SOCK_ZC_INFO_NUM; i++)
+		zc_info[i].zerocopy = INVALID_ZEROCOPY_VAL;
+}
+
 static void add_zcopy_cookie(struct msghdr *msg, uint32_t cookie)
 {
 	struct cmsghdr *cm;
@@ -183,7 +218,7 @@  static void add_zcopy_cookie(struct msghdr *msg, uint32_t cookie)
 	memcpy(CMSG_DATA(cm), &cookie, sizeof(cookie));
 }
 
-static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain)
+static bool do_sendmsg(int fd, struct msghdr *msg, int do_zerocopy, int domain)
 {
 	int ret, len, i, flags;
 	static uint32_t cookie;
@@ -201,6 +236,15 @@  static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain)
 			msg->msg_controllen = CMSG_SPACE(sizeof(cookie));
 			msg->msg_control = (struct cmsghdr *)ckbuf;
 			add_zcopy_cookie(msg, ++cookie);
+		} else if (do_zerocopy == ZC_MSGCTL_NOTIFICATION) {
+			memset(&msg->msg_control, 0, sizeof(msg->msg_control));
+			/* Although only the address of the array will be written into the
+			 * zc_ckbuf, msg_controllen must be larger or equal than any cmsg_len
+			 * in it. Otherwise, we will get -EINVAL.
+			 */
+			msg->msg_controllen = CMSG_SPACE(sizeof(zc_info));
+			msg->msg_control = (struct cmsghdr *)zc_ckbuf;
+			add_zcopy_info(msg);
 		}
 	}
 
@@ -219,7 +263,7 @@  static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain)
 		if (do_zerocopy && ret)
 			expected_completions++;
 	}
-	if (do_zerocopy && domain == PF_RDS) {
+	if (msg->msg_control) {
 		msg->msg_control = NULL;
 		msg->msg_controllen = 0;
 	}
@@ -393,6 +437,42 @@  static bool do_recvmsg_completion(int fd)
 	return ret;
 }
 
+static void do_recv_completions2(void)
+{
+	int i;
+	__u32 hi, lo, range;
+	__u8 zerocopy;
+
+	for (i = 0; zc_info[i].zerocopy != INVALID_ZEROCOPY_VAL; i++) {
+		struct zc_info_elem elem = zc_info[i];
+
+		hi = elem.hi;
+		lo = elem.lo;
+		zerocopy = elem.zerocopy;
+		range = hi - lo + 1;
+
+		if (cfg_verbose && lo != next_completion)
+			fprintf(stderr, "gap: %u..%u does not append to %u\n",
+				lo, hi, next_completion);
+		next_completion = hi + 1;
+
+		if (zerocopied == -1)
+			zerocopied = zerocopy;
+		else if (zerocopied != zerocopy) {
+			fprintf(stderr, "serr: inconsistent\n");
+			zerocopied = zerocopy;
+		}
+
+		completions += range;
+
+		if (cfg_verbose >= 2)
+			fprintf(stderr, "completed: %u (h=%u l=%u)\n",
+				range, hi, lo);
+	}
+
+	sendmsg_counter -= i;
+}
+
 static bool do_recv_completion(int fd, int domain)
 {
 	struct sock_extended_err *serr;
@@ -554,11 +634,15 @@  static void do_tx(int domain, int type, int protocol)
 		else
 			do_sendmsg(fd, &msg, cfg_zerocopy, domain);
 
-		if (cfg_zerocopy && sendmsg_counter >= cfg_notification_limit)
+		if (cfg_zerocopy == ZC_MSGERR_NOTIFICATION &&
+			sendmsg_counter >= cfg_notification_limit)
 			do_recv_completions(fd, domain);
 
+		if (cfg_zerocopy == ZC_MSGCTL_NOTIFICATION)
+			do_recv_completions2();
+
 		while (!do_poll(fd, POLLOUT)) {
-			if (cfg_zerocopy)
+			if (cfg_zerocopy == ZC_MSGERR_NOTIFICATION)
 				do_recv_completions(fd, domain);
 		}
 
@@ -716,7 +800,7 @@  static void parse_opts(int argc, char **argv)
 
 	cfg_payload_len = max_payload_len;
 
-	while ((c = getopt(argc, argv, "46c:C:D:i:l:mp:rs:S:t:vz")) != -1) {
+	while ((c = getopt(argc, argv, "46c:C:D:i:l:mnp:rs:S:t:vz")) != -1) {
 		switch (c) {
 		case '4':
 			if (cfg_family != PF_UNSPEC)
@@ -750,6 +834,9 @@  static void parse_opts(int argc, char **argv)
 		case 'm':
 			cfg_cork_mixed = true;
 			break;
+		case 'n':
+			cfg_zerocopy = ZC_MSGCTL_NOTIFICATION;
+			break;
 		case 'p':
 			cfg_port = strtoul(optarg, NULL, 0);
 			break;
@@ -769,7 +856,7 @@  static void parse_opts(int argc, char **argv)
 			cfg_verbose++;
 			break;
 		case 'z':
-			cfg_zerocopy = true;
+			cfg_zerocopy = ZC_MSGERR_NOTIFICATION;
 			break;
 		}
 	}
@@ -780,6 +867,8 @@  static void parse_opts(int argc, char **argv)
 			error(1, 0, "-D <server addr> required for PF_RDS\n");
 		if (!cfg_rx && !saddr)
 			error(1, 0, "-S <client addr> required for PF_RDS\n");
+		if (cfg_zerocopy == ZC_MSGCTL_NOTIFICATION)
+			error(1, 0, "PF_RDS does not support ZC_MSGCTL_NOTIFICATION");
 	}
 	setup_sockaddr(cfg_family, daddr, &cfg_dst_addr);
 	setup_sockaddr(cfg_family, saddr, &cfg_src_addr);
diff --git a/tools/testing/selftests/net/msg_zerocopy.sh b/tools/testing/selftests/net/msg_zerocopy.sh
index 89c22f5320e0..022a6936d86f 100755
--- a/tools/testing/selftests/net/msg_zerocopy.sh
+++ b/tools/testing/selftests/net/msg_zerocopy.sh
@@ -118,4 +118,5 @@  do_test() {
 
 do_test "${EXTRA_ARGS}"
 do_test "-z ${EXTRA_ARGS}"
+do_test "-n ${EXTRA_ARGS}"
 echo ok