Changing mfi max_cmds for new tbolt based cards?

[John Baldwin]

On Friday, November 09, 2012 9:18:17 am Steven Hartland wrote:
> I've been doing a lot of work over the past few weeks find and fixing bugs
> in the mfi driver. One of these fixes was to ensure that mfi_max_cmds is
> used consistently throughout the driver to ensure validation checks work
> as expected.
> 
> During this I noticed that mfi_max_cmds is very low for current generation
> controllers. In my case 2208 based controller reports 1008 cmd slots, so
> quite a jump from the previous max which I believe was 256?
> 
> I was wondering if we should look to change the how our sysctl is setup?
> 
> Recently John you made the following comment:
> > Mess with mfi_max_cmds at your own risk.  The limit was added to work around
> > broken mfi(4) firmware revisions that would lock up when the entire command
> > queue (256) was used.  Just a suggestion to be cautious.  It is probably
> > safe to use more than 128, but I would be wary of using all of the slots on 
> > your adapter.  (A verbose boost will show you the number of command slots your
> > firmware supports.)
> > http://lists.freebsd.org/pipermail/freebsd-current/2012-September/036639.html
> 
> Do you have an information about this specifically:-
> 1. Which generation of controller?
> 2. Which controller firmware was effected?
> 3. Was there a reproducible scenario which triggered this behaviour?
> 
> I'm going to test stability here but my current thinking is to change the
> default to -1 (controller limit) for new tbolt based controllers.
> 
> N.B. Resent from correct list account, sorry for the duplicate John.

I do not have those details, no.  I believe it was seen in earlier mfi(4)
adapters such as the parts shipped in Dell PE2950s (though knowing Dell
that probably covers a wide range of mfi(4) parts at this point).  Scott Long
is the one who added the limit in r178968 in May of 2008 (so that gives you a
bit of the timeframe for which parts were in vogue then).  I do think that
the adapters where we saw this hang used 256 command slots (may also help
narrow the relevant set of boards down).

-- 
John Baldwin