[src/trunk]: src/share/man/man4 add a warning in checksum offload that hardwa...

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

details:   https://anonhg.NetBSD.org/src/rev/23a0a35479cb
branches:  trunk
changeset: 1009002:23a0a35479cb
user:      jdolecek <jdolecek%NetBSD.org@localhost>
date:      Wed Apr 08 23:01:51 2020 +0000

description:
add a warning in checksum offload that hardware TCP segmentation might be
slow

on I219 I observe about 35% transmit performance drop when tso4 enabled

diffstat:

 share/man/man4/wm.4 |  6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diffs (27 lines):

diff -r f1939089aca3 -r 23a0a35479cb share/man/man4/wm.4
--- a/share/man/man4/wm.4       Wed Apr 08 21:57:24 2020 +0000
+++ b/share/man/man4/wm.4       Wed Apr 08 23:01:51 2020 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: wm.4,v 1.40 2018/04/13 06:04:12 msaitoh Exp $
+.\"    $NetBSD: wm.4,v 1.41 2020/04/08 23:01:51 jdolecek Exp $
 .\"
 .\" Copyright 2002, 2003 Wasabi Systems, Inc.
 .\" All rights reserved.
@@ -33,7 +33,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd April 13, 2018
+.Dd April 9, 2020
 .Dt WM 4
 .Os
 .Sh NAME
@@ -167,6 +167,8 @@
 The
 .Nm
 driver supports these features of the chip.
+At least for some chips (e.g. I219) hardware TCP segmentation is slow,
+and slows down transmit performance when turned on.
 See
 .Xr ifconfig 8
 for information on how to enable this feature.