Still confused why working set larger than virtual memory

George2 · 01-11-2008, 08:34 AM

Hello everyone,

Sorry that this question is related to another question I posted some time before because I have some new findings and self-analysis.

My question is why sometimes from perfmon on Windows, working set larger than virtual memory? I think virtual memory is the total size of memory (committed, reserved, shared, private) and working set is just the RAM touched by current process currently. Virtual memory should always larger than working set...

But, I write a simple program to show working set is larger than virtual memory from perfmon. The program is simple, just open a couple of memory map files and read from beginning to the end.

The only reason I could think of why working set sometimes is larger than virtual memory is, the OS memory management component may not reclaim some RAM consumed by current process even if the current process does not use the RAM. And keeping such RAM could improve performance if the process will use it in the future. But this point makes me confused because I think if it is true, such RAM does not have related virtual memory address, how could the current process utilize or even address (re-use to avoid hard page fault) it in the future?

thanks in advance,
George

**laserlight** · 01-11-2008, 08:38 AM

I have moved this thread to the Tech board as it does not seem to be specific to C++ programming.

iMalc · 01-11-2008, 01:12 PM

I've never seen the working set larger than the virtual size. At this stage I'm inclined to be struck with disbelief.
Care to post some numbers?
What operating system?

George2 · 01-13-2008, 02:13 AM

Hi iMalc,

I am using Windows Server 2003. I watch the working set and virtual bytes counter from perfmon of iexplorer process (IE7 browser).

It is usually the size of working set of larger than that of virtual bytes. I have uploaded the screen snapshot for your reference. It is appreciated if you could share some perspective. :-)

Quote:

Originally Posted by iMalc

I've never seen the working set larger than the virtual size. At this stage I'm inclined to be struck with disbelief.
Care to post some numbers?
What operating system?

regards,
George

George2 · 01-13-2008, 02:14 AM

Thanks laserlight,

Quote:

Originally Posted by laserlight

I have moved this thread to the Tech board as it does not seem to be specific to C++ programming.

regards,
George

01-11-2008, 08:34 AM	#1
George2 Registered User Join Date: May 2006 Posts: 1,579	Still confused why working set larger than virtual memory Hello everyone, Sorry that this question is related to another question I posted some time before because I have some new findings and self-analysis. My question is why sometimes from perfmon on Windows, working set larger than virtual memory? I think virtual memory is the total size of memory (committed, reserved, shared, private) and working set is just the RAM touched by current process currently. Virtual memory should always larger than working set... But, I write a simple program to show working set is larger than virtual memory from perfmon. The program is simple, just open a couple of memory map files and read from beginning to the end. The only reason I could think of why working set sometimes is larger than virtual memory is, the OS memory management component may not reclaim some RAM consumed by current process even if the current process does not use the RAM. And keeping such RAM could improve performance if the process will use it in the future. But this point makes me confused because I think if it is true, such RAM does not have related virtual memory address, how could the current process utilize or even address (re-use to avoid hard page fault) it in the future? thanks in advance, George
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01-11-2008, 08:38 AM	#2
laserlight C++ Witch Join Date: Oct 2003 Location: Singapore Posts: 11,339	I have moved this thread to the Tech board as it does not seem to be specific to C++ programming. __________________ C + C++ Compiler: MinGW port of GCC Build + Version Control System: SCons + Bazaar Look up a C/C++ Reference and learn How To Ask Questions The Smart Way
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01-11-2008, 01:12 PM	#3
iMalc Algorithm Dissector Join Date: Dec 2005 Location: New Zealand Posts: 2,737	I've never seen the working set larger than the virtual size. At this stage I'm inclined to be struck with disbelief. Care to post some numbers? What operating system? __________________ My homepage Advice: Take only as directed - If symptoms persist, please see your debugger
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