[PATCH net-next v5 4/4] selftests: add MSG_ZEROCOPY msg_control notification test

[zijianzhang@bytedance.com]

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 the original method approximately
aligns with the semantics of new one. 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  | 109 ++++++++++++++++++--
 tools/testing/selftests/net/msg_zerocopy.sh |   1 +
 2 files changed, 102 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/net/msg_zerocopy.c b/tools/testing/selftests/net/msg_zerocopy.c
index 7ea5fb28c93d..b8a1002aa6ae 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 +79,15 @@
 #define MSG_ZEROCOPY	0x4000000
 #endif
 
+enum notification_type {
+	MSG_ZEROCOPY_NOTIFY_ERRQUEUE = 1,
+	MSG_ZEROCOPY_NOTIFY_SENDMSG = 2,
+};
+
+#define INVALID_ZEROCOPY_VAL 2
+
+#define ZC_NOTIF_ARR_SZ (sizeof(struct zc_info_elem) * SOCK_ZC_INFO_MAX)
+
 static int  cfg_cork;
 static bool cfg_cork_mixed;
 static int  cfg_cpu		= -1;		/* default: pin to last cpu */
@@ -85,14 +99,16 @@ static bool cfg_rx;
 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_notification_limit = 16;
+static enum notification_type cfg_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 char zc_ckbuf[CMSG_SPACE(ZC_NOTIF_ARR_SZ)];
+static bool added_zcopy_info;
 static long packets, bytes, completions, expected_completions;
 static int  zerocopied = -1;
 static uint32_t next_completion;
@@ -169,6 +185,25 @@ static int do_accept(int fd)
 	return fd;
 }
 
+static void add_zcopy_info(struct msghdr *msg)
+{
+	int i;
+	struct cmsghdr *cm;
+	struct zc_info_elem *zc_info;
+
+	if (!msg->msg_control)
+		error(1, errno, "NULL user arg");
+	cm = (struct cmsghdr *)msg->msg_control;
+	zc_info = (struct zc_info_elem *)CMSG_DATA(cm);
+
+	cm->cmsg_len = CMSG_LEN(ZC_NOTIF_ARR_SZ);
+	cm->cmsg_level = SOL_SOCKET;
+	cm->cmsg_type = SCM_ZC_NOTIFICATION;
+	for (i = 0; i < SOCK_ZC_INFO_MAX; i++)
+		zc_info[i].zerocopy = INVALID_ZEROCOPY_VAL;
+	added_zcopy_info = true;
+}
+
 static void add_zcopy_cookie(struct msghdr *msg, uint32_t cookie)
 {
 	struct cmsghdr *cm;
@@ -182,7 +217,8 @@ 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,
+			   enum notification_type do_zerocopy, int domain)
 {
 	int ret, len, i, flags;
 	static uint32_t cookie;
@@ -200,6 +236,12 @@ 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 == MSG_ZEROCOPY_NOTIFY_SENDMSG &&
+			   sends_since_notify >= cfg_notification_limit) {
+			memset(&msg->msg_control, 0, sizeof(msg->msg_control));
+			msg->msg_controllen = sizeof(zc_ckbuf);
+			msg->msg_control = (struct cmsghdr *)zc_ckbuf;
+			add_zcopy_info(msg);
 		}
 	}
 
@@ -218,7 +260,7 @@ 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;
 	}
@@ -392,6 +434,48 @@ static bool do_recvmsg_completion(int fd)
 	return ret;
 }
 
+static void do_recv_completions2(void)
+{
+	int i;
+	__u32 hi, lo, range;
+	__u8 zerocopy;
+	struct cmsghdr *cm = (struct cmsghdr *)zc_ckbuf;
+	struct zc_info_elem *zc_info = (struct zc_info_elem *)CMSG_DATA(cm);
+
+	if (!added_zcopy_info)
+		return;
+
+	added_zcopy_info = false;
+	for (i = 0; i < SOCK_ZC_INFO_MAX && 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);
+	}
+
+	sends_since_notify -= i;
+}
+
 static bool do_recv_completion(int fd, int domain)
 {
 	struct sock_extended_err *serr;
@@ -553,11 +637,15 @@ static void do_tx(int domain, int type, int protocol)
 		else
 			do_sendmsg(fd, &msg, cfg_zerocopy, domain);
 
-		if (cfg_zerocopy && sends_since_notify >= cfg_notification_limit)
+		if (cfg_zerocopy == MSG_ZEROCOPY_NOTIFY_ERRQUEUE &&
+			sends_since_notify >= cfg_notification_limit)
 			do_recv_completions(fd, domain);
 
+		if (cfg_zerocopy == MSG_ZEROCOPY_NOTIFY_SENDMSG)
+			do_recv_completions2();
+
 		while (!do_poll(fd, POLLOUT)) {
-			if (cfg_zerocopy)
+			if (cfg_zerocopy == MSG_ZEROCOPY_NOTIFY_ERRQUEUE)
 				do_recv_completions(fd, domain);
 		}
 
@@ -715,7 +803,7 @@ 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)
@@ -749,6 +837,9 @@ static void parse_opts(int argc, char **argv)
 		case 'm':
 			cfg_cork_mixed = true;
 			break;
+		case 'n':
+			cfg_zerocopy = MSG_ZEROCOPY_NOTIFY_SENDMSG;
+			break;
 		case 'p':
 			cfg_port = strtoul(optarg, NULL, 0);
 			break;
@@ -768,7 +859,7 @@ static void parse_opts(int argc, char **argv)
 			cfg_verbose++;
 			break;
 		case 'z':
-			cfg_zerocopy = true;
+			cfg_zerocopy = MSG_ZEROCOPY_NOTIFY_ERRQUEUE;
 			break;
 		}
 	}
@@ -779,6 +870,8 @@ 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 == MSG_ZEROCOPY_NOTIFY_SENDMSG)
+			error(1, 0, "PF_RDS does not support MSG_ZEROCOPY_NOTIFY_SENDMSG");
 	}
 	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