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From: ted@cgl.ucsf.edu@blia.UUCP
Newsgroups: mod.computers.vax
Subject: Re: PIDs -- curiosity
Message-ID: <8701141843.AA06014@blia.BLI>
Date: Wed, 14-Jan-87 13:43:43 EST
Article-I.D.: blia.8701141843.AA06014
Posted: Wed Jan 14 13:43:43 1987
Date-Received: Fri, 16-Jan-87 22:18:02 EST
References: <8701131650.AA08077@ucbvax.Berkeley.EDU>
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Summary: Version 4.x External and Internal PIDs

In article <8701131650.AA08077@ucbvax.Berkeley.EDU>, SYNFUL@DRYCAS.BITNET (Marc Shannon) writes:
> After this was done, I noticed that the PID for SWAPPER was 00000010.
> Normally (when I ran 4.3 before and when I was running 4.4) it was
> 00000040.  After I installed a few more packages, SWAPPER returned
> to its normal 00000040.
> On our 8650 running V4.4 (and recently clustered), the PIDs are
> 2140xxxx (now, anyway...sometime before I could have sworn they
> were 2040xxxx).

This is all due to the format of version 4.x external PIDs. The format of
the longword is as follows:

	|                      |                  |                   |
	| cluster node #       | IPID sequence #  | IPID slot #       |
	|     (10 bits)        |    (22-n bits)   |      (n bits)     |
	|                      |                  |                   |

where the "IPID sequence #" is the high word of the internal PID (equiv. to
the version 3.x PID), "IPID slot #" is the low word of the internal PID, and
"n" is the minimum number of bits required to hold the process slot number as
determined from the SYSGEN maximum number of processes.

Thus, the high 10 bits contains the node number (0 on a non-clustered VAX),
the low "n" bits contains the process slot number (just as many bits as
required), and the remaining bits contain the sequence number for the
process slot. Since the swapper is slot # 1, sequence # 1, on a system
configured for 15 or fewer processes and not in a cluster, its pid would
be 00000011. Reconfiguring the system for 32 to 63 processes would change
it to 00000041. (I assume your saying the swapper was in 10 and 40 was a typo.
Either you meant the null process or you meant 11 and 41). Your big VAX
has its node number in the high bits and so its PIDs are 214xxxxx.

The PID conversion routines are in the module SYSPCTRL in facility SYS if
you want to look at the fiche. These routines are described on page 8-12
of the version 4.0 release notes (you did keep the 4.0 release notes, didn't
you? :->).

===============================================================================
            Ted Marshall
            Britton Lee, Inc.
p-mail:     14600 Winchester Blvd, Los Gatos, Ca 95030
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disclaimer: These opinions are my own and may not reflect those of my employer;
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fortune for today:
Churchill's Commentary on Man:
	Man will occasionally stumble over the truth, but most of the
	time he will pick himself up and continue on.