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Re: [apple scitech] Real v. Virtual Memory Footprint



That was almost too simple.  Thanks.



At 4:12 PM -0800 11/30/07, Rich Cook wrote:
Again, google is your friend.  Just search for it.

http://developer.apple.com/documentation/Performance/Conceptual/ManagingMemory/Articles/AboutMemory.html#//apple_ref/doc/uid/20001880-119066-TPXREF102

On Nov 30, 2007, at 4:03 PM, Kenneth Prager wrote:

I understand the virtual memory operation but I don't get why the virtual memory footprint, for a given application, grows (seemingly without bound) over time. I can't be the only one seeing their system go from one to many swap files over a few days time. The reduction in performance is annoying.

Regards,

Ken Prager



At 11:04 AM -0800 11/30/07, Rich Cook wrote:
It's because your application is reserving memory but not looking at most of it. What happens is that OS X swaps things in RAM out to disk when they are not recently used. Do a google on "how virtual memory works" to understand more.

On Nov 30, 2007, at 9:59 AM, Kenneth Prager wrote:

I have a question regarding an application's real memory footprint versus its virtual memory footprint. I am asking this question here because (a) I know that there are many knowledgeable people here and (b) I honestly don't know which other of the Apple lists is more appropriate (is this a Darwin question, a Cocoa question, etc.). Also, I am asking this question only because I am curious, not because I expect to do anything with the information.

Here is my question: when I reboot my Mac, it starts out with one swap file (BTW, I have 2 GB of RAM). If I look at memory usage in the Activity Monitor, real and virtual memory footprints are the same. After about a week I am typically up to 5 or 6 swap files and for most applications, the virtual memory footprint is 10-15 times as large as the real memory footprint (for example, PCalc's real footprint is 6.7 MB and virtual footprint is 364.5 MB).

Why is this? Is it because of a lack of garbage collection in Objective C? If so, will the addition of garbage collection in Leopard automatically solve this problem?

Thanks in advance,

Ken Prager




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References: 
 >[apple scitech] Real v. Virtual Memory Footprint (From: Kenneth Prager <email@hidden>)
 >Re: [apple scitech] Real v. Virtual Memory Footprint (From: Rich Cook <email@hidden>)
 >Re: [apple scitech] Real v. Virtual Memory Footprint (From: Kenneth Prager <email@hidden>)
 >Re: [apple scitech] Real v. Virtual Memory Footprint (From: Rich Cook <email@hidden>)



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