Author: julian
Date: Fri Dec 2 08:24:00 2016
New Revision: 309402
URL: https://svnweb.freebsd.org/changeset/base/309402
Log:
MFH: r309295
bhyve: stability and performance improvement for dbgport
The TCP server implementation in dbgport does not track clients, so it
may try to write to a disconected socket resulting in SIGPIPE.
Avoid that by setting SO_NOSIGPIPE socket option.
Because dbgport emulates an I/O port to guest, the communication is done
byte by byte. Reduce latency of the TCP/IP transfers by using
TCP_NODELAY option. In my tests that change improves performance of
kgdb commands with lots of output (e.g. info threads) by two orders of
magnitude.
A general note. Since we have a uart emulation in bhyve, that can be
used for the console and gdb access to guests. So, bvmconsole and bvmdebug
could be de-orbited now. But there are many existing deployments that
still dependend on those.
Discussed with: julian, jhb
Sponsored by: Panzura
Modified:
stable/11/usr.sbin/bhyve/dbgport.c
Directory Properties:
stable/11/ (props changed)
Modified: stable/11/usr.sbin/bhyve/dbgport.c
==============================================================================
--- stable/11/usr.sbin/bhyve/dbgport.c Fri Dec 2 08:21:25 2016
(r309401)
+++ stable/11/usr.sbin/bhyve/dbgport.c Fri Dec 2 08:24:00 2016
(r309402)
@@ -32,6 +32,7 @@ __FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
+#include <netinet/tcp.h>
#include <sys/uio.h>
#include <stdio.h>
@@ -55,8 +56,9 @@ static int
dbg_handler(struct vmctx *ctx, int vcpu, int in, int port, int bytes,
uint32_t *eax, void *arg)
{
- char ch;
int nwritten, nread, printonce;
+ int on = 1;
+ char ch;
if (bytes == 2 && in) {
*eax = BVM_DBG_SIG;
@@ -74,8 +76,16 @@ again:
printonce = 1;
}
conn_fd = accept4(listen_fd, NULL, NULL, SOCK_NONBLOCK);
- if (conn_fd < 0 && errno != EINTR)
+ if (conn_fd >= 0) {
+ /* Avoid EPIPE after the client drops off. */
+ (void)setsockopt(conn_fd, SOL_SOCKET, SO_NOSIGPIPE,
+ &on, sizeof(on));
+ /* Improve latency for one byte at a time tranfers. */
+ (void)setsockopt(conn_fd, IPPROTO_TCP, TCP_NODELAY,
+ &on, sizeof(on));
+ } else if (errno != EINTR) {
perror("accept");
+ }
}
if (in) {
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