File 2601-erts-Free-udp-buffer-when-getting-EAGAIN.patch of Package erlang

From 83445d0de88a1ad15066e6c415b2c2d9aa93d6a1 Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas@erlang.org>
Date: Wed, 20 Jun 2018 17:54:24 +0200
Subject: [PATCH 1/2] erts: Free udp buffer when getting EAGAIN

Only SCPT should keep the recv buffer when going into
select. If UDP does it, it will result in many more
memory allocations than there should be which can be
very detrimental to performance.
---
 erts/emulator/drivers/common/inet_drv.c | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/erts/emulator/drivers/common/inet_drv.c b/erts/emulator/drivers/common/inet_drv.c
index 5e9afdc5ca..833befefd1 100644
--- a/erts/emulator/drivers/common/inet_drv.c
+++ b/erts/emulator/drivers/common/inet_drv.c
@@ -1785,6 +1785,7 @@ static void release_buffer(ErlDrvBinary* buf)
 #ifdef HAVE_UDP
 static ErlDrvBinary* realloc_buffer(ErlDrvBinary* buf, ErlDrvSizeT newsz)
 {
+    DEBUGF(("realloc_buffer: %ld -> %ld\r\n", (buf==NULL) ? 0 : buf->orig_size, newsz));
     return driver_realloc_binary(buf, newsz);
 }
 #endif
@@ -12042,15 +12043,11 @@ static int packet_inet_input(udp_descriptor* udesc, HANDLE event)
 	sys_memzero((char *) &other, sizeof(other));
 
 	/* udesc->i_buf is only kept between SCTP fragments */
-	if (udesc->i_buf == NULL) {
-	    udesc->i_bufsz = desc->bufsz + len;
-	    if ((udesc->i_buf = alloc_buffer(udesc->i_bufsz)) == NULL)
-		return packet_error(udesc, ENOMEM);
-	    /* pointer to message start */
-	    udesc->i_ptr = udesc->i_buf->orig_bytes + len;
-	} else {
-	    ErlDrvBinary* tmp;
+#ifdef HAVE_SCTP
+	if (udesc->i_buf != NULL) {
+            ErlDrvBinary* tmp;
 	    int bufsz;
+            ASSERT(IS_SCTP(desc));
 	    bufsz = desc->bufsz + (udesc->i_ptr - udesc->i_buf->orig_bytes);
 	    if ((tmp = realloc_buffer(udesc->i_buf, bufsz)) == NULL) {
 		release_buffer(udesc->i_buf);
@@ -12062,6 +12059,15 @@ static int packet_inet_input(udp_descriptor* udesc, HANDLE event)
 		udesc->i_buf = tmp;
 		udesc->i_bufsz = bufsz;
 	    }
+	} else
+#endif
+        {
+            ASSERT(udesc->i_buf == NULL);
+	    udesc->i_bufsz = desc->bufsz + len;
+	    if ((udesc->i_buf = alloc_buffer(udesc->i_bufsz)) == NULL)
+		return packet_error(udesc, ENOMEM);
+	    /* pointer to message start */
+	    udesc->i_ptr = udesc->i_buf->orig_bytes + len;
 	}
 
 	/* Note: On Windows NT, recvfrom() fails if the socket is connected. */
@@ -12120,6 +12126,14 @@ static int packet_inet_input(udp_descriptor* udesc, HANDLE event)
 		) {
 		sock_select(desc,FD_READ,1);
 	    }
+#ifdef HAVE_SCTP
+            if (!short_recv) {
+#endif
+                release_buffer(udesc->i_buf);
+                udesc->i_buf = NULL;
+#ifdef HAVE_SCTP
+            }
+#endif
 	    return count;		/* strange, not ready */
 	}
 
-- 
2.16.4