Bugs

[Ronald S H Khoo]

jallen at eeserv1.ic.sunysb.edu (Joseph Allen) writes:

> >Why not use pipes instead?
> Because how do you make a pipe between unrelated processes?

With the mknod command or system call, and the open system call.
Named pipes have been in UNIX since System III at least.
SCO Xenix documentation has a section on in in the "writing and using pipes"
section of the Programmer's Guide.  The pipe appears in the filesystem
so anyone can open it.

> Also I've found that the message passing system calls are very fast (I don't
> have experience with streams but BSD sockets were always a bit slow).

There is *zero* difference in speed between using pipes and using
message queues.  The reason is that the IPC overhead is completely
swamped by the cost of the context switch.  If you write a program
that forks two processes, which does this:

	Process 1		Process 2

	Send message
				Receive message
				Send message
	Receive message

in a loop, you will find that the number of transactions that you can do in
any given time frame is about the same no matter which IPC mechanism you
use.  Context switching in 386 Unixes is *AWFUL*.  BAD BAD BAD.  Terrible.
You could do the IPC by carrier pigeon and and the transaction rate would
*still* be the same.  Ugh.  <Shudder>

This is probably a good reason to switch to Mach.  Anyone want to
volunteer some figures for this on Mach 386?

> I seem to remember that there's supposed to be a SCO uucp site.  Are these
> fixes there, and if so, how do I contact the site?

Machine name: sosco
Phone numbers: (408) 425-3502 (2 lines, 300-9600 baud V.32 standard)
	       (408) 429-1786 (9600 baud Telebit)
Login name: uusls   (fourth character is the letter "l" rather than numeral "1")
No password

Get the file /usr/spool/uucppublic/SLS/info.
This information is posted here from time to time by SCO people.
What they *don't* post is the fact that the file
/usr/spool/uucppublic/SLS/descriptions
is also a useful file to grab.  The info file doesn't say so either.

It might do in the future, I told the Nice Man[TM] from SCO about it last week
when he came to visit.

-- 
[TM]  Nice Man may well be a trademark of the Automobile Association
-- 
Ronald Khoo <ronald at robobar.co.uk> +44 81 991 1142 (O) +44 71 229 7741 (H)