datapath: Add module parameter to allow TSO with vlans.

[openvswitch] / INSTALL.Linux

diff --git a/INSTALL.Linux b/INSTALL.Linux
index e950c05197b868ee69fa02ec2796c6f490ce0b43..f80e1c645fec5b30c5d438dd1df7a8c02f7529ae 100644 (file)
--- a/INSTALL.Linux
+++ b/INSTALL.Linux
@@ -227,6 +227,17 @@ Prerequisites section, follow the procedure below to build.
         module loading, please include the output from the "dmesg" and
         "modinfo" commands mentioned above.
 
+   There is an optional module parameter to openvswitch_mod.ko called
+   vlan_tso that enables TCP segmentation offload over VLANs on NICs
+   that support it. Many drivers do not expose support for TSO on VLANs
+   in a way that Open vSwitch can use but there is no way to detect
+   whether this is the case. If you know that your particular driver can
+   handle it (for example by testing sending large TCP packets over VLANs)
+   then passing in a value of 1 may improve performance. Modules built for
+   Linux kernels 2.6.37 and later do not need this and do not have this
+   parameter. If you do not understand what this means or do not know if
+   your driver will work, do not set this.
+
 7. Initialize the configuration database using ovsdb-tool, e.g.:
 
       % ovsdb-tool create /usr/local/etc/ovs-vswitchd.conf.db vswitchd/vswitch.ovsschema