Subject: Re: RFH: serial port benchmarking
To: Garrett D'Amore <>
From: Garrett D'Amore <>
List: tech-kern
Date: 06/23/2006 08:36:43
Daniel Carosone wrote:
> On Tue, Jun 20, 2006 at 11:55:27AM -0700, Garrett D'Amore wrote:
>> I'm looking for someone who can help benchmark UART performance to
>> compare gdamore-uart and -current.  I suspect that the differences will
>> be small, but I've been asked to provide some more concrete numbers,
>> particularly of interest is i386 hardware, for which I do not have ready
>> access. 
> I did some archeology, and dug up some old machines.  I have something
> that I think is an 8Mb 33Mhz 486, and that still seems to power on and
> POST get to the PRESS F1 TO CONTINUE prompt.  I'm not going to get
> past this for a while, because it has a large-style AT DIN keyboard
> plug, and I seem to have nothing functional to plug into it now.
> It probably still has some ancient NetBSD, perhaps 0.9-ish era, on the
> 2x200Mb SCSI disks that seem to still both spin up.  I hope so, that
> will make the problem of getting code onto it easier.

Thanks.  I probably can scrounge a large style->small style keyboard
adapter.  What I don't know is whether it is for plugging a small
keyboard in a large hole or vice versa.  I'll check and get back to you.

>> (I also don't know how best to collect such performance data on
>> i386 -- are there processor performance counters that can be used?)
> My plan would be to set up some back-to-back serial transfers with a
> modern machine, and crank up the serial speed until it starts to spew
> about silo overflows.  If the current and branch kernels start failing
> at different speeds, i'd call the effect noticable.  Suggestions for
> other tests that I can perform without too much effort welcome.

That sounds like a good idea to me.

>> Also, if anyone has com(4) ports that are marginal at performance, it
>> would be great to test them to verify that I haven't made things any
>> worse. :-)
> I found a whole lot of ISA serial cards, at least one with big chunky
> 83450's on, probably others.  It's not impossible that I have a HAYESP
> around somewhere, too.

Cool.  Thanks for the help, btw!

    -- Garrett
> --
> Dan.

Garrett D'Amore, Principal Software Engineer
Tadpole Computer / Computing Technologies Division,
General Dynamics C4 Systems
Phone: 951 325-2134  Fax: 951 325-2191