Re: Basic virtual memory question

From: JF Mezei (jfmezei.spamnot_at_teksavvy.com)
Date: 01/07/05 

Date: Fri, 07 Jan 2005 15:46:01 -0500

Bob Koehler wrote:

> At the SYSGEN level things are limited by VIRTUALPAGECNT and WSMAX.

SYSGEN's help tells me that VirtualPageCnt has been obsolete since version 7.0.

What prevents me from giving a 200 meg PGFILQUO to a username and have a
process created that then does a MALLOC of 200 megabytes on a 16 meg Microvax
II ?

> IIRC the process page table is sized at process creation according to
> VIRTUALPAGECNT.

Ok, so each process has its own page table then ?

How does VMS size that page table ? (seems it used to be VIRTUALPAGCNT that
answered that question, but is now obsolete).

> PAGEDYN and NPAGEDYN limit kernel memory pools, not process memory.

Howeber, any physical memory that is alloacted to system structures is memory
that cannot be used by processes to map their virtual pages to physical pages,
correct ?

> No. There is a parameter PHYSICALPAGES which can be set to prevent
> VMS from mapping pages that look like RAM but are not actually memory,

I thought PHYSICAL PAGES was to simulate a system with less memory that it
really has.

> No process or combination of processes should be limited to the
> physical RAM size of the computer in any virtual memory OS.

yes, but what determines the virtual memory limit a process can think it has
access to ? If I give it a PAGFILQUO of 200 megs, (and there is 200 megs
available in the page file), is there another parameter that woudl prevent the
procesxs from using 200 megs ?

Relevant Pages

  • Re: Basic virtual memory question
    ... If Working sets grow larger than page file quota, ... > SYSGEN's help tells me that VirtualPageCnt has been obsolete since version 7.0. ... >> PAGEDYN and NPAGEDYN limit kernel memory pools, ... There is a parameter PHYSICALPAGES which can be set to prevent ...
    (comp.os.vms)
  • Re: Storing system files in CMS
    ... I'd think you've run out of a memory ... > resource. ... You may have to increase VIRTUALPAGECNT. ... ...and/or the PGFLQUOTA of the account from which you are executing the command. ...
    (comp.os.vms)
  • Re: Basic virtual memory question
    ... John Reagan wrote: ... >> SYSGEN's help tells me that VirtualPageCnt has been obsolete since ... >> What prevents me from giving a 200 meg PGFILQUO to a username and have a ...
    (comp.os.vms)
  • Re: Basic virtual memory question
    ... > JF Mezei wrote: ... >> SYSGEN's help tells me that VirtualPageCnt has been obsolete since version 7.0. ... >> What prevents me from giving a 200 meg PGFILQUO to a username and have a ...
    (comp.os.vms)
  • Re: Basic virtual memory question
    ... >> At the SYSGEN level things are limited by VIRTUALPAGECNT and WSMAX. ... >SYSGEN's help tells me that VirtualPageCnt has been obsolete since version 7.0. ... You should have read on a bit further, where it says "on Alpha systems". ...
    (comp.os.vms)