netdev - [PATCH net-next 2/3] selftests: fix OOM problem in msg

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Message-Id: <20240409205300.1346681-3-zijianzhang@bytedance.com>
Date: Tue,  9 Apr 2024 20:52:59 +0000
From: zijianzhang@...edance.com
To: netdev@...r.kernel.org
Cc: edumazet@...gle.com,
	willemdebruijn.kernel@...il.com,
	davem@...emloft.net,
	kuba@...nel.org,
	cong.wang@...edance.com,
	xiaochun.lu@...edance.com,
	Zijian Zhang <zijianzhang@...edance.com>
Subject: [PATCH net-next 2/3] selftests: fix OOM problem in msg_zerocopy selftest

From: Zijian Zhang <zijianzhang@...edance.com>

In selftests/net/msg_zerocopy.c, it has a while loop keeps calling sendmsg
on a socket, and it will recv the completion notifications when the socket
is not writable. Typically, it will start the receiving process after
around 30+ sendmsgs.

However, because of the commit dfa2f0483360
("tcp: get rid of sysctl_tcp_adv_win_scale"), the sender is always writable
and does not get any chance to run recv notifications. The selftest always
exits with OUT_OF_MEMORY because the memory used by opt_skb exceeds
the core.sysctl_optmem_max. We introduce "cfg_notification_limit" to
force sender to receive notifications after some number of sendmsgs. Plus,
in the selftest, we need to update skb_orphan_frags_rx to be the same as
skb_orphan_frags. In this case, for some reason, notifications do not
come in order now. We introduce "cfg_notification_order_check" to
possibly ignore the checking for order.

Signed-off-by: Zijian Zhang <zijianzhang@...edance.com>
Signed-off-by: Xiaochun Lu <xiaochun.lu@...edance.com>
---
 tools/testing/selftests/net/msg_zerocopy.c | 24 ++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/net/msg_zerocopy.c b/tools/testing/selftests/net/msg_zerocopy.c
index bdc03a2097e8..8e595216a0af 100644
--- a/tools/testing/selftests/net/msg_zerocopy.c
+++ b/tools/testing/selftests/net/msg_zerocopy.c
@@ -85,6 +85,8 @@ static bool cfg_rx;
 static int  cfg_runtime_ms	= 4200;
 static int  cfg_verbose;
 static int  cfg_waittime_ms	= 500;
+static bool cfg_notification_order_check;
+static int  cfg_notification_limit = 32;
 static bool cfg_zerocopy;
 
 static socklen_t cfg_alen;
@@ -435,7 +437,7 @@ static bool do_recv_completion(int fd, int domain)
 	/* Detect notification gaps. These should not happen often, if at all.
 	 * Gaps can occur due to drops, reordering and retransmissions.
 	 */
-	if (lo != next_completion)
+	if (cfg_notification_order_check && lo != next_completion)
 		fprintf(stderr, "gap: %u..%u does not append to %u\n",
 			lo, hi, next_completion);
 	next_completion = hi + 1;
@@ -489,7 +491,7 @@ static void do_tx(int domain, int type, int protocol)
 		struct iphdr iph;
 	} nh;
 	uint64_t tstop;
-	int fd;
+	int fd, sendmsg_counter = 0;
 
 	fd = do_setup_tx(domain, type, protocol);
 
@@ -548,10 +550,18 @@ static void do_tx(int domain, int type, int protocol)
 			do_sendmsg_corked(fd, &msg);
 		else
 			do_sendmsg(fd, &msg, cfg_zerocopy, domain);
+		sendmsg_counter++;
+
+		if (sendmsg_counter == cfg_notification_limit && cfg_zerocopy) {
+			do_recv_completions(fd, domain);
+			sendmsg_counter = 0;
+		}
 
 		while (!do_poll(fd, POLLOUT)) {
-			if (cfg_zerocopy)
+			if (cfg_zerocopy) {
 				do_recv_completions(fd, domain);
+				sendmsg_counter = 0;
+			}
 		}
 
 	} while (gettimeofday_ms() < tstop);
@@ -708,7 +718,7 @@ static void parse_opts(int argc, char **argv)
 
 	cfg_payload_len = max_payload_len;
 
-	while ((c = getopt(argc, argv, "46c:C:D:i:mp:rs:S:t:vz")) != -1) {
+	while ((c = getopt(argc, argv, "46c:C:D:i:mp:rs:S:t:vzol:")) != -1) {
 		switch (c) {
 		case '4':
 			if (cfg_family != PF_UNSPEC)
@@ -760,6 +770,12 @@ static void parse_opts(int argc, char **argv)
 		case 'z':
 			cfg_zerocopy = true;
 			break;
+		case 'o':
+			cfg_notification_order_check = true;
+			break;
+		case 'l':
+			cfg_notification_limit = strtoul(optarg, NULL, 0);
+			break;
 		}
 	}
 
-- 
2.20.1