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If the incomplete listen queue for a given socket is full,

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drop the oldest entry in the queue.

There was a fair bit of discussion as to whether or not the
proper action is to drop a random entry in the queue.  It's
my conclusion that a random drop is better than a head drop,
however profiling this section of code (done by John Capo)
shows that a head-drop results in a significant performance
increase.

There are scenarios where a random drop is more appropriate.
If I find one in reality, I'll add the random drop code under
a conditional.

Obtained from: discussions and code done by Vernon Schryver (vjs@sgi.com).
This commit is contained in:
pst 1996-09-20 21:25:18 +00:00
parent 6b0658e42a
commit dd5375bf7c
2 changed files with 36 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
sys/netinet/tcp_input.c
View File

@ -31,7 +31,7 @@
* SUCH DAMAGE.
*
* @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
* $Id: tcp_input.c,v 1.47 1996/09/13 18:47:03 pst Exp $
* $Id: tcp_input.c,v 1.48 1996/09/13 23:51:41 pst Exp $
*/
#ifndef TUBA_INCLUDE
@ -410,11 +410,24 @@ findpcb:
#endif
if (so->so_options & SO_ACCEPTCONN) {
register struct tcpcb *tp0 = tp;
so = sonewconn(so, 0);
if (so == 0) {
tcpstat.tcps_listendrop++;
goto drop;
struct socket *so2;
/*
* If the attempt to get onto the socket queue failed,
* drop the oldest queue entry and try again.
*/
so2 = sonewconn(so, 0);
if (!so2) {
so2 = TAILQ_FIRST(&so->so_incom);
if (so2) {
tcp_drop(sototcpcb(so2), ETIMEDOUT);
so2 = sonewconn(so, 0);
}
if (!so2) {
tcpstat.tcps_listendrop++;
goto drop;
}
}
so = so2;
/*
* This is ugly, but ....
*

23
sys/netinet/tcp_reass.c
View File

@ -31,7 +31,7 @@
* SUCH DAMAGE.
*
* @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
* $Id: tcp_input.c,v 1.47 1996/09/13 18:47:03 pst Exp $
* $Id: tcp_input.c,v 1.48 1996/09/13 23:51:41 pst Exp $
*/
#ifndef TUBA_INCLUDE
@ -410,11 +410,24 @@ findpcb:
#endif
if (so->so_options & SO_ACCEPTCONN) {
register struct tcpcb *tp0 = tp;
so = sonewconn(so, 0);
if (so == 0) {
tcpstat.tcps_listendrop++;
goto drop;
struct socket *so2;
/*
* If the attempt to get onto the socket queue failed,
* drop the oldest queue entry and try again.
*/
so2 = sonewconn(so, 0);
if (!so2) {
so2 = TAILQ_FIRST(&so->so_incom);
if (so2) {
tcp_drop(sototcpcb(so2), ETIMEDOUT);
so2 = sonewconn(so, 0);
}
if (!so2) {
tcpstat.tcps_listendrop++;
goto drop;
}
}
so = so2;
/*
* This is ugly, but ....
*