svn commit: r348473 - head/sys/netinet/netdump

[Mark Johnston]

Author: markj
Date: Fri May 31 18:29:12 2019
New Revision: 348473
URL: https://svnweb.freebsd.org/changeset/base/348473

Log:
  netdump: Buffer pages to avoid calling netdump_send() on each 4KB write.
  
  netdump waits for acknowledgement from the server for each write.  When
  dumping page table pages, we perform many small writes, limiting
  throughput.  Use the netdump client's buffer to buffer small contiguous
  writes before calling netdump_send() to flush the MAXDUMPPGS-sized
  buffer.  This results in a significant reduction in the time taken to
  complete a netdump.
  
  Submitted by:	Sam Gwydir <sam at samgwydir.com>
  Reviewed by:	cem
  MFC after:	2 weeks
  Differential Revision:	https://reviews.freebsd.org/D20317

Modified:
  head/sys/netinet/netdump/netdump_client.c

Modified: head/sys/netinet/netdump/netdump_client.c
==============================================================================
--- head/sys/netinet/netdump/netdump_client.c	Fri May 31 18:00:44 2019	(r348472)
+++ head/sys/netinet/netdump/netdump_client.c	Fri May 31 18:29:12 2019	(r348473)
@@ -130,6 +130,9 @@ static struct {
 	union kd_ip	 ndc_client;
 	union kd_ip	 ndc_gateway;
 	uint8_t		 ndc_af;
+	/* Runtime State */
+	off_t		 nd_tx_off;
+	size_t		 nd_buf_len;
 } nd_conf;
 #define	nd_server	nd_conf.ndc_server.in4
 #define	nd_client	nd_conf.ndc_client.in4
@@ -945,6 +948,14 @@ netdump_dumper(void *priv __unused, void *virtual,
 	    virtual, (uintmax_t)offset, length);
 
 	if (virtual == NULL) {
+		if (nd_conf.nd_buf_len != 0) {
+			error = netdump_send(NETDUMP_VMCORE, nd_conf.nd_tx_off, nd_buf,
+			    nd_conf.nd_buf_len);
+			if (error != 0) {
+				dump_failed = 1;
+			}
+		}
+
 		if (dump_failed != 0)
 			printf("failed to dump the kernel core\n");
 		else if (netdump_send(NETDUMP_FINISHED, 0, NULL, 0) != 0)
@@ -957,12 +968,22 @@ netdump_dumper(void *priv __unused, void *virtual,
 	if (length > sizeof(nd_buf))
 		return (ENOSPC);
 
-	memmove(nd_buf, virtual, length);
-	error = netdump_send(NETDUMP_VMCORE, offset, nd_buf, length);
-	if (error != 0) {
-		dump_failed = 1;
-		return (error);
+	if (nd_conf.nd_buf_len + length > sizeof(nd_buf) || 
+	    (nd_conf.nd_buf_len != 0 && nd_conf.nd_tx_off + 
+	    nd_conf.nd_buf_len != offset)) {
+		error = netdump_send(NETDUMP_VMCORE, nd_conf.nd_tx_off, nd_buf, 
+		    nd_conf.nd_buf_len);
+		if (error != 0) {
+			dump_failed = 1;
+			return (error);
+		}
+		nd_conf.nd_buf_len = 0;
+		nd_conf.nd_tx_off = offset;
 	}
+
+	memmove(nd_buf + nd_conf.nd_buf_len, virtual, length);
+	nd_conf.nd_buf_len += length;
+
 	return (0);
 }