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Decrease lock contention within the TCP accept case by removing

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the INP_INFO lock from tcp_usr_accept.  As the PR/patch states
this was following the advice already in the code.
See the PR below for a full disucssion of this change and its
measured effects.

PR:		183659
Submitted by:	Julian Charbon
Reviewed by:	jhb
This commit is contained in:
George V. Neville-Neil 2014-01-28 20:28:32 +00:00
parent 3a6cdc4e55
commit 6f3caa6d81
2 changed files with 3 additions and 10 deletions
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4
sys/netinet/tcp_syncache.c
View File

@ -682,7 +682,7 @@ syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
* connection when the SYN arrived. If we can't create
* the connection, abort it.
*/
so = sonewconn(lso, SS_ISCONNECTED);
so = sonewconn(lso, 0);
if (so == NULL) {
/*
* Drop the connection; we will either send a RST or
@ -922,6 +922,8 @@ syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
INP_WUNLOCK(inp);
soisconnected(so);
TCPSTAT_INC(tcps_accepts);
return (so);

9
sys/netinet/tcp_usrreq.c
View File

@ -610,13 +610,6 @@ tcp_usr_disconnect(struct socket *so)
/*
* Accept a connection. Essentially all the work is done at higher levels;
* just return the address of the peer, storing through addr.
*
* The rationale for acquiring the tcbinfo lock here is somewhat complicated,
* and is described in detail in the commit log entry for r175612. Acquiring
* it delays an accept(2) racing with sonewconn(), which inserts the socket
* before the inpcb address/port fields are initialized. A better fix would
* prevent the socket from being placed in the listen queue until all fields
* are fully initialized.
*/
static int
tcp_usr_accept(struct socket *so, struct sockaddr **nam)
@ -633,7 +626,6 @@ tcp_usr_accept(struct socket *so, struct sockaddr **nam)
inp = sotoinpcb(so);
KASSERT(inp != NULL, ("tcp_usr_accept: inp == NULL"));
INP_INFO_RLOCK(&V_tcbinfo);
INP_WLOCK(inp);
if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
error = ECONNABORTED;
@ -653,7 +645,6 @@ tcp_usr_accept(struct socket *so, struct sockaddr **nam)
out:
TCPDEBUG2(PRU_ACCEPT);
INP_WUNLOCK(inp);
INP_INFO_RUNLOCK(&V_tcbinfo);
if (error == 0)
*nam = in_sockaddr(port, &addr);
return error;