Hi,
When running tcpbench -su, a lot of them are counted as "missed PCB
cache".
I reboot the computer then netstat -sp udp gives
udp:
10 datagrams received
0 with incomplete header
0 with bad data length field
0 with bad checksum
0 with no checksum
0 input packets software-checksummed
0 output packets software-checksummed
0 dropped due to no socket
0 broadcast/multicast datagrams dropped due to no socket
0 dropped due to missing IPsec protection
0 dropped due to full socket buffers
10 delivered
14 datagrams output
0 missed PCB cache
I run tcpbench -su and use a client and I netstat -sp udp again :
udp:
1086364 datagrams received
0 with incomplete header
0 with bad data length field
0 with bad checksum
0 with no checksum
0 input packets software-checksummed
0 output packets software-checksummed
0 dropped due to no socket
3 broadcast/multicast datagrams dropped due to no socket
0 dropped due to missing IPsec protection
1201 dropped due to full socket buffers
1085160 delivered
14 datagrams output
1086351 missed PCB cache
After the bind(2), a PCB is created with a wildcard source address which
is not a direct match for incoming packets which means that we need to
perform a second lookup to find the "listener PCB". And the connect(2)
creates a new PCB for this connection thus avoiding a second lookup.
Patch with (a lot of) help from mikeb@
Reboot the laptop and run the test again:
udp:
1074985 datagrams received
0 with incomplete header
0 with bad data length field
0 with bad checksum
0 with no checksum
0 input packets software-checksummed
0 output packets software-checksummed
0 dropped due to no socket
1 broadcast/multicast datagram dropped due to no socket
0 dropped due to missing IPsec protection
1295 dropped due to full socket buffers
1073689 delivered
14 datagrams output
6 missed PCB cache
Index: tcpbench.c
===================================================================
RCS file: /cvs/src/usr.bin/tcpbench/tcpbench.c,v
retrieving revision 1.42
diff -u -p -r1.42 tcpbench.c
--- tcpbench.c 19 Aug 2014 03:28:53 -0000 1.42
+++ tcpbench.c 29 Aug 2014 14:22:35 -0000
@@ -610,8 +610,17 @@ udp_server_handle_sc(int fd, short event
{
ssize_t n;
struct statctx *sc = v_sc;
+ struct sockaddr_storage ss;
+ socklen_t slen;
- n = read(fd, ptb->dummybuf, ptb->dummybuf_len);
+ /* If this was our first packet, perform a connect */
+ if (mainstats.peak_mbps == 0) {
+ n = recvfrom(fd, ptb->dummybuf, ptb->dummybuf_len, 0,
+ (struct sockaddr *)&ss, &slen);
+ if (n > 0 && connect(fd, (const struct sockaddr *)&ss, slen))
+ warn("fail to connect");
+ } else
+ n = read(fd, ptb->dummybuf, ptb->dummybuf_len);
if (n == 0)
return;
else if (n == -1) {
