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RE: Preemptive patch for etrax kernel?



You are correct that you can't expect to get a response
within a few milliseconds. Other customers have made
various modifications to get fast serial port repsonse
e.g:

1. Use the fast DMA flush timer in kernelconfig.
2. Decrease the scheduler time slot.

Even if you implement these or other fixes you can never
rely on the timing for the reply. There are other
applications and interrupts that also needs to run.

/Mikael

-----Original Message-----
From: owner-dev-etrax@xxxxxxx.com]On">mailto:owner-dev-etrax@xxxxxxx.com]On
Behalf Of Pieter Grimmerink
Sent: Wednesday, April 03, 2002 11:02 AM
To: dev-etrax
Subject: RE: Preemptive patch for etrax kernel?



> On Tue, 2 Apr 2002, Pieter Grimmerink wrote:
> > What would be the chances of getting a preemptive schedular patch
> > working on the etrax kernel?
> > Has anyone ever tried this, or can anyone predict what would
> > be necessary to port any of the available patches?
> 
> If you say what you're going to use it for, maybe we or others on 
> the list 
> can recommend other ways than trying those patches.

My main concern is for an application where we are a slave on a serial bus
via a normal comport, and therefore have to respond to commands within 
a few milliseconds.
I fear the standard linux kernel will not be responsive enough, and I'd
rather not have to implement much of the protocol in a kernelmodule in 
order to be able to respond in time.

I don't think you can call this requirement a hard realtime one, and I
don't look forward to porting any of the realtime patches...
So I was hoping a preemptive schedular might already provide enough 
responsiveness for such applications.

Best regards,

Pieter Grimmerink