[comp.unix.questions] Keeping up with 19200 baud

urlichs@smurf.ira.uka.de (Matthias Urlichs) (11/18/89)

I have the following problem with my Macintosh II, running A/UX 1.0 (S5R2):

When receiving 19200 baud data with uucp-g, the speed is OK at first. Then
things start to deteriorate; it seems that uucico doesn't get processor time
when its read is complete but some time afterwards (about 1/5 to 1/10 second).
As soon as I start a disk-intensive job, uucico's speed goes up, then down
again a few seconds after the disk intensive job is completed. (I used
find / -name vgztw ;-) 

nice(-20) doesn't do anything except that the speed drops off somewhat slower.
ps shows a NICE of zero (obviously) and PRI goes up to 70 rather fast.
It also shows a C parameter of 10.
This seems to indicate that the scheduler thinks my uucico is CPU-bound when
in reality it is emphatically not. (Sending goes ahead at full speed which I
can't explain because it should not make a difference to the scheduler
whether I send a block of 64 bytes and read one of five, or the other way
round).

What can I do?
Can I (comp.unix.questions question) access the kernel's process structure in
kernel memory and set the PRI and/or C values back to something "reasonable"?
Any sample code to access the proc table which actually works? :-)

Or (comp.unix.aux question) is that problem fixed in A/UX 1.1?

aTdHvAnKcSe
-- Matthias Urlichs, urlichs@smurf.ira.uka.de

alexis@panix.UUCP (Alexis Rosen) (11/28/89)

This is not my field of expertise, but I believe that the Mac's built-in
serial ports can't begin to cope with 19.2kbps because they get an interrupt
for every byte. If so, either your statistics are wrong, or you're using a
serial card.

So: Am I wrong? If not, are you? If not, what card are you using?

Alexis Rosen
alexis@rascal.ics.utexas.edu