Module Name: src
Committed By: jdolecek
Date: Fri Apr 24 22:07:13 UTC 2020
Modified Files:
src/sys/kern: uipc_mbuf.c
Log Message:
change m_defrag() to coalesce the chain to single mbuf if it's short enough
and first mbuf doesn't use external storage
most fragmented packets end up with first short mbuf containing
frame + protocol header only, and second mbuf containing the data;
m_defrag() previously always returned chain of at least two mbufs,
now it should actually return all data in single mbuf for typical
mbuf chain with length < MCLBYTES
To generate a diff of this commit:
cvs rdiff -u -r1.237 -r1.238 src/sys/kern/uipc_mbuf.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/uipc_mbuf.c
diff -u src/sys/kern/uipc_mbuf.c:1.237 src/sys/kern/uipc_mbuf.c:1.238
--- src/sys/kern/uipc_mbuf.c:1.237 Sun Mar 15 23:14:41 2020
+++ src/sys/kern/uipc_mbuf.c Fri Apr 24 22:07:12 2020
@@ -1,4 +1,4 @@
-/* $NetBSD: uipc_mbuf.c,v 1.237 2020/03/15 23:14:41 thorpej Exp $ */
+/* $NetBSD: uipc_mbuf.c,v 1.238 2020/04/24 22:07:12 jdolecek Exp $ */
/*
* Copyright (c) 1999, 2001, 2018 The NetBSD Foundation, Inc.
@@ -62,7 +62,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uipc_mbuf.c,v 1.237 2020/03/15 23:14:41 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uipc_mbuf.c,v 1.238 2020/04/24 22:07:12 jdolecek Exp $");
#ifdef _KERNEL_OPT
#include "opt_mbuftrace.h"
@@ -1672,6 +1672,40 @@ m_defrag(struct mbuf *m, int how)
if (m->m_next == NULL)
return m;
+ /* Defrag to single mbuf if at all possible */
+ if ((m->m_flags & M_EXT) == 0) {
+ if (m->m_pkthdr.len <= MHLEN) {
+ if (M_TRAILINGSPACE(m) < (m->m_pkthdr.len - m->m_len)) {
+ KASSERT(M_LEADINGSPACE(m) >=
+ (m->m_pkthdr.len - m->m_len));
+ memmove(m->m_pktdat, m->m_data, m->m_len);
+ m->m_data = m->m_pktdat;
+ }
+
+ KASSERT(M_TRAILINGSPACE(m) >=
+ (m->m_pkthdr.len - m->m_len));
+ if (__predict_false(!m_ensure_contig(&m,
+ m->m_pkthdr.len))) {
+ panic("m_ensure_contig(%d) failed\n",
+ m->m_pkthdr.len);
+ }
+ return m;
+ } else if (m->m_pkthdr.len <= MCLBYTES) {
+ void *odata = m->m_data;
+
+ MCLGET(m, how);
+ if ((m->m_flags & M_EXT) == 0)
+ return NULL;
+ memcpy(m->m_data, odata, m->m_len);
+ if (m_pulldown(m, m->m_len, m->m_pkthdr.len - m->m_len,
+ NULL) == NULL) {
+ panic("m_pulldown(%d, %d) failed\n",
+ m->m_len, m->m_pkthdr.len - m->m_len);
+ }
+ return m;
+ }
+ }
+
m0 = m_get(how, MT_DATA);
if (m0 == NULL)
return NULL;
