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From: nagy%warner.hepnet@LBL.ARPA
Newsgroups: comp.os.vms
Subject: RE: PID's across VAXClusters
Message-ID: <870910062958.027@Lbl.Arpa>
Date: Thu, 10-Sep-87 09:29:57 EDT
Article-I.D.: Lbl.870910062958.027
Posted: Thu Sep 10 09:29:57 1987
Date-Received: Sat, 12-Sep-87 11:25:13 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 40

>Does anyone know how you can relate the first few digits of the PID
>to the cluster node you are on? I'd like to be able to tell which
>account file I'm looking at by the PID's of the processes therein.
     
The following was pulled from the SYS$LIBRARY:LIB.REQ file (under VMS V4.5):

! 
! *** WARNING - THE INTERNAL STRUCTURE OF THE EPID IS SUBJECT TO RADICAL
! ***           CHANGE BETWEEN VERSIONS OF VMS.  NO ASSUMPTIONS SHOULD
! ***           EVER BE MADE ABOUT ITS FORMAT
! 

PCB$V_EPIC_PROC		size=21 bits	offset=bit 0
			! PROCESS ID FIELD, CAN CONVERT TO PCB$L_PID

PCB$V_EPID_NODE_IDX	size=8 bits	offset=bit 21
			! IDX - INDEX TO TABLE OF NODE IDENTIFICATIONS

PCB$V_EPID_NODE_SEQ	size=2 bits	offset=bit 29
			! SEQ - SEQUENCE NUMBER FOR NODE TABLE ENTRY REUSE

PCB$V_EPID_WILD		size=1 bit	offset=bit 31
			! FLAG THAT EPID IS WILDCARD CONTEXT FOR $GETJPI,
			! AND NOT A VALID EPID

So, the node is represented in the EPID (External or Extended PID), by
an index into a table.  I believe that nodes are added to the table in
the order they join the VAXCluster.  Thus the node identified by a particular
slot in the table can possibly change from boot to boot.  My interpretation
of this is that the EPID is not useful in determining which processor a
process ran on in the past; only which processor it is running on at the
present time (present incarnation of the VAXCluster after a boot).



= Frank J. Nagy   "VAX Guru"
= Fermilab Research Division EED/Controls
= HEPNET: WARNER::NAGY (43198::NAGY) or FNAL::NAGY (43009::NAGY)
= BitNet: NAGY@FNAL
= USnail: Fermilab POB 500 MS/220 Batavia, IL 60510