[Samba] What controls the Read AndX Request byte size?

Steven Cardinal steven.cardinal at gmail.com
Fri Sep 29 18:31:33 GMT 2006

On 9/29/06, Jeremy Allison <jra at samba.org> wrote:
> On Fri, Sep 29, 2006 at 08:45:08AM -0400, Steven Cardinal wrote:
> > In trying to track down some performance issues, I'm finding with
> Ethereal
> > that, when I launch an application from my Windows server, the SMB Read
> AndX
> > Request packets have Min Count, Max Count Low, and Remaining all at 512
> > bytes. When launching the same application on the same client from a
> Win2000
> > share, these requests are coming in much larger sizes (4096 and 32768
> were
> > both observed). This is making a huge difference in the launch speed of
> the
> > application (an in-house VB app).
> >
> > My question is, what smb.conf or kernel parameters could be influencing
> the
> > 512 byte read request? I tried setting various socket options in
> > smb.confand haven't seen a change. I am running Suse
> > 10.0 with their 3.0.20b samba packages (except we recompiled to include
> > idmap_rid).
> Looks like Windows has decided you're on a WAN link, not a
> LAN link. I'd check MSDN on the web for registry settings
> affecting this. (Can't remember them offhand).
> Jeremy.

Problem solved. It was, in fact, the kernel oplocks. I didn't realize that
Samba needed to be fully restarted (and not just HUPped) for this param to
take effect. Disabling kernel oplocks on my test box and restarting removed
the issue. I will implement the change this weekend on my production box.

Thanks for your attention. And especially thanks to the guy who posted about
ARCView a few weeks back!

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