[src/trunk]: src/sys/netinet As suggested by at least 3 different people (the...

[tls <tls%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/26feef511170
branches:  trunk
changeset: 753543:26feef511170
user:      tls <tls%NetBSD.org@localhost>
date:      Thu Apr 01 01:23:32 2010 +0000

description:
As suggested by at least 3 different people (the guilty parties know who
they are) avoid repeated kernel_lock/unlock by using an intrq on the stack.

About 5%-10% better from run to run, on my *very* simpleminded test.  Can't
possibly be worse.

diffstat:

 sys/netinet/ip_input.c |  30 +++++++++++++++++++++++-------
 1 files changed, 23 insertions(+), 7 deletions(-)

diffs (67 lines):

diff -r 686f94c83c16 -r 26feef511170 sys/netinet/ip_input.c
--- a/sys/netinet/ip_input.c    Thu Apr 01 01:11:53 2010 +0000
+++ b/sys/netinet/ip_input.c    Thu Apr 01 01:23:32 2010 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ip_input.c,v 1.285 2010/03/31 07:31:15 tls Exp $       */
+/*     $NetBSD: ip_input.c,v 1.286 2010/04/01 01:23:32 tls Exp $       */
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -91,7 +91,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ip_input.c,v 1.285 2010/03/31 07:31:15 tls Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ip_input.c,v 1.286 2010/04/01 01:23:32 tls Exp $");
 
 #include "opt_inet.h"
 #include "opt_compat_netbsd.h"
@@ -231,6 +231,7 @@
 int    in_multientries;                        /* total number of addrs */
 struct in_multihashhead *in_multihashtbl;
 struct ifqueue ipintrq;
+
 uint16_t ip_id;
 
 percpu_t *ipstat_percpu;
@@ -474,20 +475,35 @@
 {
        int s;
        struct mbuf *m;
+       struct ifqueue lcl_intrq;
+
+       memset(&lcl_intrq, 0, sizeof(lcl_intrq));
+       ipintrq.ifq_maxlen = ipqmaxlen;
 
        mutex_enter(softnet_lock);
        KERNEL_LOCK(1, NULL);
-       while (!IF_IS_EMPTY(&ipintrq)) {
+       if (!IF_IS_EMPTY(&ipintrq)) {
                s = splnet();
-               IF_DEQUEUE(&ipintrq, m);
+
+               /* Take existing queue onto stack */
+               lcl_intrq = ipintrq;
+
+               /* Zero out global queue, preserving maxlen and drops */
+               ipintrq.ifq_head = NULL;
+               ipintrq.ifq_tail = NULL;
+               ipintrq.ifq_len = 0;
+               ipintrq.ifq_maxlen = lcl_intrq.ifq_maxlen;
+               ipintrq.ifq_drops = lcl_intrq.ifq_drops;
+
                splx(s);
+       }
+       KERNEL_UNLOCK_ONE(NULL);
+       while (!IF_IS_EMPTY(&lcl_intrq)) {
+               IF_DEQUEUE(&lcl_intrq, m);
                if (m == NULL)
                        break;
-               KERNEL_UNLOCK_ONE(NULL);
                ip_input(m);
-               KERNEL_LOCK(1, NULL);
        }
-       KERNEL_UNLOCK_ONE(NULL);
        mutex_exit(softnet_lock);
 }