Operating System - OpenVMS
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Process Affinity

Occasional Contributor

Process Affinity

I have a strange behavior regarding process affinity on OpenVMS IA64 8.3. The parameter SCH_HARD_OFFLD is 1-3 (4 active CPU's). I start a detached process $run/deta/out=a.txt dir:b.exe. I would think that the process would be limited to CPU 0 due to the sysgen parameter but actually I see it on all 4 CPU's.
A $show cpu/full shows that this process is not manually affinitized. Any ideas appreciated.
Volker Halle
Honored Contributor

Re: Process Affinity

According to the HP OpenVMS Version 8.3--1H1
for Integrity Servers New Features and Release Notes chapter 3.4.2 HP OpenVMS Version 8.3 New Features and Documentation Overview

'Also, because of a technical issue, the SCH_HARD_OFFLD parameter is no longer used starting in OpenVMS V8.3.'

This may explain the behaviour you've seen.

John Gillings
Honored Contributor

Re: Process Affinity

Note that affinity isn't very well documented. There is functionality that hasn't yet made it into HELP or the DCL Dictionary.

Maybe next release of the docs will explain it all. In the mean time, contact your local Customer Support Centre to get more detail on what you can do with SET PROCESS/AFFINITY.
A crucible of informative mistakes

Re: Process Affinity

$! dedicate.com
$! p1 is the CPU to be dedicated
$ if p1 .eqs. "" then inquire p1
$ set process /priority=63
$ set process /affinity /set='p1' /perm
$ loop: goto loop

For example;

$ set device BG0: /preferred_cpus=19
$ spawn /nowait /notify @dedicate 19