- Community Home
- >
- Servers and Operating Systems
- >
- Operating Systems
- >
- Operating System - OpenVMS
- >
- Another question about Global Pages
Categories
Company
Local Language
Forums
Discussions
Forums
- Data Protection and Retention
- Entry Storage Systems
- Legacy
- Midrange and Enterprise Storage
- Storage Networking
- HPE Nimble Storage
Discussions
Discussions
Discussions
Forums
Forums
Discussions
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
- BladeSystem Infrastructure and Application Solutions
- Appliance Servers
- Alpha Servers
- BackOffice Products
- Internet Products
- HPE 9000 and HPE e3000 Servers
- Networking
- Netservers
- Secure OS Software for Linux
- Server Management (Insight Manager 7)
- Windows Server 2003
- Operating System - Tru64 Unix
- ProLiant Deployment and Provisioning
- Linux-Based Community / Regional
- Microsoft System Center Integration
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Discussion Boards
Community
Resources
Forums
Blogs
- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Printer Friendly Page
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО08-19-2005 04:36 AM
тАО08-19-2005 04:36 AM
GS1280
Fact #1:
========
$ install list/glo/sum
Galaxy Group Global Sections
1298 Global Sections Used, 36254432/255685040 Global Pagelets Used/Unused
Fact #2:
========
sho mem/phy
System Memory Resources on 19-AUG-2005 09:31:31.96
Physical Memory Usage (pages): Total Free In Use Modified
Main Memory (64.00GB) 8388608 2402302 5649259 337047
What gives?
===========
From Fact #1:
- 36254432 pagelets used = about 18GB mem
(very reasonable)
- 255685040 pagelets free = about 128GB mem,
yet Fact #2 shows we only have 64GB total!
Can someone explain this to me? Thanks.
Solved! Go to Solution.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО08-19-2005 04:44 AM
тАО08-19-2005 04:44 AM
Re: Another question about Global Pages
the 'V' in VMS stands for 'Virtual' Memory System.
Global Pages can be paged and don't need to occupy physical pages.
Volker.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО08-20-2005 08:09 PM
тАО08-20-2005 08:09 PM
Re: Another question about Global Pages
use sh mem command as follow
$ SHOW MEM/UNIT=BYTE/PHYS !Physical pages
$ SHOW MEM/UNIT=BYTE/FILES !Virtual mem
I guess you can understand why you virtual memory is greater than physical memory.
Antonio Vigliotti
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО08-20-2005 09:00 PM
тАО08-20-2005 09:00 PM
Solutionglobal pages are an OpenVMS memory management construct to allow several processes to share parts of their virtual address space.
If a process references a global page, which is not yet in physical memory, it has to be loaded into memory from it's backing store (global page fault). If another process then accesses the same global page, it just has to be made valid in his workingset (global valid fault). Using global pages saves physical memory and pagefault IOs.
Note that there could also be global pages physically locked into memory (memory resident global sections - see the SYSMAN RESERVED_MEMORY commands or the $CRMPSC_GDZRO_64 system service).
Volker.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО08-20-2005 10:15 PM
тАО08-20-2005 10:15 PM
Re: Another question about Global Pages
Process private and global pages are essentially differ in scope, not concept. Process private pages are private to an individual process, global pages are available to multiple processes. These differing classes of pages appear in different areas of your process' address space (see the "OpenVMS Programming Concepts Manual", available in PDF and HTML from the OpenVMS www site at http://www.hp.com/go/openvms; there is also a good description of the issues surrounding global sections in various chapters of the Internals and Data Structures books -- the general concepts have not changed extensively in a VERY long time).
With either process-private or global pages, you can (and I can argue, should) have more virtual memory than real memory in most cases. This is the reason for the advent of virtual memory about 40 years ago. In short, much of the program and data used by a program is not used often, if ever. Before the advent of virtual memory, and on machines not supporting virtual memory, program controlled overlaying (of code and data) was used to fit applications into machines. It was a grueling process. Virtual memory removes that laborious process to the operating system. When information is needed, it is paged in. When information has not been used for an extended time, the "page" containing the information (if it is writeable) is written to the temporary backing store (aka, the page file) and the memory is recycled. Generally speaking, this is an efficient process, and not a problem. When paging becomes excessive, this leads to a performance problem referred to as "thrashing". There is a wealth of pre-VMS literature on the issues surrounding paging, in journals such as those published by the ACM (www.acm.org) and IEEE (www.ieee.org). There are also some classic books covering the origins of paging, including that by Bell and Sieworiek (my apologies to Dan Sieworiek if I have mis-spelled his name, I don't have the book handy).
The amount of virtual memory to real memory is referred to (appropriately enough) the virtual to real ratio. The suitability of a specific virtual to real ratio is workload dependant. 2:1 is not a particularly high ratio for a timesharing workload.
My apologies for the long post, I hope that the background is useful.
- Bob Gezelter, http://www.rlgsc.com
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО08-21-2005 07:16 PM
тАО08-21-2005 07:16 PM
Re: Another question about Global Pages
You are not the first one that is supprised.
Check http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=855313
Wim
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
тАО08-22-2005 08:58 AM
тАО08-22-2005 08:58 AM
Re: Another question about Global Pages
Years back I just presumed that the output from the INSTALL LIST cmd was refering to physical pages. Now I know better!