socket options

Scott Lovenberg scott.lovenberg at
Wed Feb 20 14:47:21 MST 2013

On Wed, Feb 20, 2013 at 4:27 PM, Andrew Bartlett <abartlet at> wrote:
> On Wed, 2013-02-20 at 16:15 -0500, Scott Lovenberg wrote:
>> On Sun, Feb 17, 2013 at 4:11 AM, Andrew Bartlett <abartlet at> wrote:
>> > Would you like to write a patch to at least improve the warnings in 'man
>> > smb.conf'?  Probably not ascii-art, but some clear text explaining why
>> > this should be the last, not first resort, particularly on Linux.
>> >
>> > Thanks,
>> >
>> > Andrew Bartlett
>> How about this wording?  If everyone is ok with it, I'll format it for
>> a man page and submit it as a patch (since the mailing list hates
>> non-plain text).
>> "
>> Warning:
>> "Premature optimization is the root of all evil." -- Donald Knuth
>> Changing socket options should be attempted only after consulting the
>> Samba Performance Tuning chapter of _The Official Samba HOWTO and
>> Reference Guide_
>> (
>> and exhausting all other means of improving performance.
> The problem with linking to that document is that it is more a source of
> confusion and outdated information than a solution to it.
> I'm actually in a mood to totally remove it, or if not to gut it,
> because I have no indication (in the commit logs) that it has had any
> significant attention to technical detail in 10 (probably more like 15)
> years.  (Notice it compares with NT, and mentions NetBEUI as a common
> network protocol...).
I just actually read through the entire section.  It is very dated.
I'm not sure it is relevant any more and I'd understand if you removed
it entirely.

>> 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.
>> 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 test the effect before making any large
>> changes.
>> "
>> Is this wording acceptable?  I could definitely drop the Knuth quote,
>> but I think it sets the tone perfectly for socket tuning.  Plus, I
>> like to quote Knuth.
> Otherwise, I like it.  Perhaps we start with just the last two
> paragraphs (and the quote, if you can find the right docbook syntax).

That works for me.  I'll write it up.

Peace and Blessings,

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