Kernel mode programming -precisions

[Ryan Sommers]

Street Chaman wrote:

> Thanks to everyone who read my question; here some precisions:
> 
> Actually, my soft is a kind of interactive filter: it takes a lot of 
> imput parameters (from keyboard at the moment, but as soon as i've 
> understood how it works, i will increase the number of supported io 
> devices); treats it in a particular way and produces an output. This 
> 'particular way' requires a lot of clock cycle, so speed is my first 
> problem; (that's part of reason why everything is directly written in 
> assembly). I've already buffered input and output, but only as far at it 
> was possible: since loop (X) input could affect loop (X-1) general data 
> manipulation, and change output, it must be detected quickly. The time 
> needed to read/write is still to long. When CPU is waiting on some new 
> data, he cannot preform any other operation, and freezes data 
> manipultion; that's why I'm looking for a new way to in/output the soft...
> I've found out in syscall.master the aio_read/write call. Man page says 
> operation is asynchronous, so it returns quite immediatly after 
> enqueuing the io thread. Could that be a solution ?  Or back to kernel 
> module (by the way: is it possible to write on in assembly) ?

I don't think you're supplying us with enough information here to give 
you a definitive answer. You mention reading from the keyboard but then 
you say that it can't read/write fast enough? You must be one hellofa 
typist. What are you reading/writing from? Keyboard? Disks? 
Reading/writing to disks is going to be slow, the kernel buffer caches 
will help though. Why is it so critical that syscalls return faster than 
they are? Are you attempting to do real-time computing? Are you doing 
any kind of threading? Is it even physically possible to return faster 
on the IO device you are wishing to access?

You mention doing it all in assembly, have you tried coding the same 
thing in C with a select few (as someone else mentioned) critical paths 
written in assembly? You could then more easily make use of 
multi-threading the application on an SMP box. However, this is all 
blind conjecture because we have relatively little information about 
what you are trying to accomplish.

-- 
Ryan Sommers
ryans at gamersimpact.com