Re: [Vacm-general] Slow EMP handling

['Ard v. Breemen' <ar...@te...>]

On Wed, Jul 25, 2001 at 08:24:15AM -0700, San Mehat wrote:
> The first thing I did when I got my cyclades was open it up :) Ted Tso,
Of course :)
> the author of the Linux TTY/serial driver layer also had a look.. It
> appears they use a *ton* of semi-standard UARTS which are connected to
> an ISA bus on the system... fine for normal bursted serial flow.. but
ugh...
> really awfull for lots of single byte I/O which is what the EMP state
> machine calls for rather heavily.... 
Hmmm.... Actually it should be workable...
A kernel "thread" should poll all emp ports (I guess half of them will be
emp, the other half will be serial console) in a single poll stroke.
That is about 1920 poll's per second no matter the number of ports.
Any active port will result in the emp-daemon being scheduled at most
1920 times per second, no matter the number of ports. In a single stroke
the emp-daemon should be able to respond to all traffic, and queue any
incoming data from the emp ports.
That is 500 microseconds for kernel-interrupt, task switch, and handling
of data. Of course, the task switch only happens when it was not already
running.
After that, a more normal threaded and buffered approach can be used.
>   This has been a common problem with serial concentrator vendors.... in
> any event, playing in the kernel may be difficult as I understand their
> serial driver itself is not open source.... other than that I agree that
Grrrr. Although, the CDK is a .i386.rpm, but it looks like it contains
source.
> it may be just a matter of software, however I just don't have the
> bandwidth to work on yet another piece of serial hardware (I'm currently
> working on preliminary IPMI 1.5 over LAN support)
Eh, that is ipmi with default lan support?
> If you do decide to take this on, let me know.. I'd be happy to provide
> whatever EMP related assistance I can...
Well, I first have to search for a cyclades first...
I will probably not be able to obtain one :( , so I will try to think out
my bike computer some more.  (bike sample http://www.alleweder.nl )
(Ever seen a bike computer that show median speed instead of that stupid
average?)
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