Re: ANN: VMTester - virtual memory testing utility

FROM : Ben Dougall
DATE : Wed Apr 06 00:08:43 2005

On Tuesday, April 5, 2005, at 10:44  pm, Cameron Hayne wrote:

>
> But so far, I find that it is proving some of my previous statements 
> wrong -
> those about the "inactive" memory.  Of course, it's not entirely my 
> fault
> since I was just repeating what Apple has said in its developer docs
> (http://developer.apple.com/documentation/Performance/Conceptual/
> ManagingMem
> ory/Concepts/AboutMemory.html) and in this relatively recent article on
> Activity Monitor: http://docs.info.apple.com/article.html?artnum=107918
>
> When I allocate memory using my VMTester app, I see that it is adding 
> to the
> "inactive" list. I had expected to see it added to the "active" list 
> instead


i think it's like this:
allocating it just ear marks it -- you don't actually, physically get 
the memory when you allocate it. when you make use of it, that's when 
things actually happen. so i think if you were to allocate 100mb of 
memory not a lot happens, apart from you now have the right to use 
100mb of memory. when and if you use, say just 1mb of that 100mb, 
that's when things actually happen. that's when real memory (1mb) is 
taken over by your app. it allocates on actual access/use -- puts 
allocation off to the last possible moment basically i think.