Documentation: Add a warning to "socket options"

 Add a warning to the "socket options" section of the
 smb.conf man page that changing socket options can be
 dangerous to performance.  Hopefully this will cut down on
 users reporting poor performance after changing socket
 options.

Signed-off-by: Scott Lovenberg <scott.lovenberg@gmail.com>

Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/docs-xml/smbdotconf/tuning/socketoptions.xml b/docs-xml/smbdotconf/tuning/socketoptions.xml
index 7a5c221939..27ae5fd32b 100644
--- a/docs-xml/smbdotconf/tuning/socketoptions.xml
+++ b/docs-xml/smbdotconf/tuning/socketoptions.xml
@@ -4,6 +4,23 @@
                  developer="1"
                  xmlns:samba="http://www.samba.org/samba/DTD/samba-doc">
 <description>
+    <para>
+        <warning>
+        <para>Modern server operating systems are tuned for high
+        network performance in the majority of situations; when you set socket
+        options you are overriding those settings.  Linux in particular has an
+        auto-tuning mechanism for buffer sizes that will be disabled if you
+        specify a socket buffer size.  This can potentially cripple your
+        TCP/IP stack.</para>
+
+        <para> Getting the socket options correct can make a big difference to
+        your performance, but getting them wrong can degrade it by just as
+        much.  As with any other low level setting, if you must make changes
+        to it, make small changes and <emphasis>test</emphasis> the effect
+        before making any large changes.</para>
+        </warning>
+    </para>
+
     <para>This option allows you to set socket options 
     to be used when talking with the client.</para>