From e5f4acdbb7669644d8c751056f3aa2e7bf684460 Mon Sep 17 00:00:00 2001
From: Srujana <skanchisamud@nvidia.com>
Date: Tue, 30 Jul 2024 20:39:33 +0000
Subject: [PATCH] lib: Memory spike reduction for sh cmds at scale
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The output buffer vty->obuf is a linked list where
each element is of 4KB.
Currently, when a huge sh command  like “show ip route json”
is executed on a large scale, all the vty_out’s are
processed and the entire data is accumulated.
After the entire vty execution, vtysh_flush proceeses
and puts this data in the socket (131KB at a time).

Problem here is the memory spike for such heavy duty
show commands.

The fix here is to chunkify the output on VTY shell by
flushing it intermediately for every 128 KB of output
accumulated and free the memory allocated for the buffer data.

This way, we achieve ~25-30% reduction in the memory spike.

Signed-off-by: Rajasekar Raja <rajasekarr@nvidia.com>
Signed-off-by: Srujana <skanchisamud@nvidia.com>
---
 lib/vty.c     | 25 +++++++++++++++++++++++++
 lib/vty.h     |  7 +++++++
 vtysh/vtysh.c | 16 ++++++++++++++++
 vtysh/vtysh.h |  1 +
 4 files changed, 49 insertions(+)

diff --git a/lib/vty.c b/lib/vty.c
index d0bbf0e61a5c..0d2580389862 100644
--- a/lib/vty.c
+++ b/lib/vty.c
@@ -345,8 +345,17 @@ int vty_out(struct vty *vty, const char *format, ...)
 	case VTY_SHELL_SERV:
 	case VTY_FILE:
 	default:
+		vty->vty_buf_size_written += strlen(filtered);
 		/* print without crlf replacement */
 		buffer_put(vty->obuf, (uint8_t *)filtered, strlen(filtered));
+		/* For every chunk of memory, we invoke vtysh_flush where we
+		 * put the data of collective vty->obuf Linked List items on the
+		 * socket and free the vty->obuf data.
+		 */
+		if (vty->vty_buf_size_written >= MAX_INTERMEDIATE_FLUSH) {
+			vty->vty_buf_size_written = 0;
+			vtysh_flush(vty);
+		}
 		break;
 	}
 
@@ -2141,6 +2150,21 @@ static void vtysh_accept(struct event *thread)
 		close(sock);
 		return;
 	}
+	/* Setting the SND buffer size to 16MB to increase the buffer size
+	 * the socket can hold before sending it to VTY shell
+	 */
+	uint32_t sndbufsize = SEND_BUF_MAX;
+	int ret;
+
+	ret = setsockopt(sock, SOL_SOCKET, SO_SNDBUF, (char *)&sndbufsize,
+			 sizeof(sndbufsize));
+	if (ret < 0) {
+		flog_err(EC_LIB_SOCKET,
+			 "Cannot set socket %d send buffer size, %s", sock,
+			 safe_strerror(errno));
+		close(sock);
+		return;
+	}
 	set_cloexec(sock);
 
 #ifdef VTYSH_DEBUG
@@ -2227,6 +2251,7 @@ static int vtysh_flush(struct vty *vty)
 		vty_close(vty);
 		return -1;
 	case BUFFER_EMPTY:
+		vty->vty_buf_size_written = 0;
 		break;
 	}
 	return 0;
diff --git a/lib/vty.h b/lib/vty.h
index c336a816cc1f..4be77dabd86b 100644
--- a/lib/vty.h
+++ b/lib/vty.h
@@ -236,6 +236,7 @@ struct vty {
 	uintptr_t mgmt_req_pending_data;
 	bool mgmt_locked_candidate_ds;
 	bool mgmt_locked_running_ds;
+	uint64_t vty_buf_size_written;
 };
 
 static inline void vty_push_context(struct vty *vty, int node, uint64_t id)
@@ -338,6 +339,12 @@ struct vty_arg {
 /* Vty read buffer size. */
 #define VTY_READ_BUFSIZ 512
 
+/* Vty max send buffer size (4096 * 4096). */
+#define SEND_BUF_MAX 16777216
+
+/* Vty flush intermediate size (32 * 4096). */
+#define MAX_INTERMEDIATE_FLUSH 131072
+
 /* Directory separator. */
 #ifndef DIRECTORY_SEP
 #define DIRECTORY_SEP '/'
diff --git a/vtysh/vtysh.c b/vtysh/vtysh.c
index e657aa8af0ac..bd1bfd8424c2 100644
--- a/vtysh/vtysh.c
+++ b/vtysh/vtysh.c
@@ -4721,6 +4721,22 @@ static int vtysh_connect(struct vtysh_client *vclient)
 		close(sock);
 		return -1;
 	}
+	/* Setting the RCV buffer size to 16MB to increase the buffer size
+	 * the socket can hold after receving from other process
+	 */
+	uint32_t rcvbufsize = RCV_BUF_MAX;
+
+	ret = setsockopt(sock, SOL_SOCKET, SO_RCVBUF, (char *)&rcvbufsize,
+			 sizeof(rcvbufsize));
+	if (ret < 0) {
+#ifdef DEBUG
+		fprintf(stderr, "Cannot set socket %d rcv buffer size, %s\n",
+			sock, safe_strerror(errno));
+#endif /* DEBUG */
+		close(sock);
+		return -1;
+	}
+
 	vclient->fd = sock;
 
 	return 0;
diff --git a/vtysh/vtysh.h b/vtysh/vtysh.h
index b1d57aa3c221..76d4d766482d 100644
--- a/vtysh/vtysh.h
+++ b/vtysh/vtysh.h
@@ -35,6 +35,7 @@ extern struct event_loop *master;
 #define VTYSH_PATHD     0x80000
 #define VTYSH_PIM6D     0x100000
 #define VTYSH_MGMTD 0x200000
+#define RCV_BUF_MAX	16777216
 
 #define VTYSH_WAS_ACTIVE (-2)