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Memory usage

Posted on 2002-03-18
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Last Modified: 2007-11-27
Hi

Can anybody explain this.

I have a crappy delphi app. which uses around 12 MB.
When I minimize it, it drops to use about one MB, that I understand fine. But when I maximize it again it only uses 3 MB. What has happend ? is there a 9MB memory leak which Windows have cleaned up for me ?
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Question by:bnz
12 Comments
 
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by:raidos
ID: 6876864
No, When you minimize the App Windows decides to put most data of that process into the Swap, and when you Restore it Windows doesn't crunch up all the data, until it is actually needed...

Regards
//raidos
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by:geobul
ID: 6877161
Hi,
What's the memory usage immediately after starting that app?

Possible situation: Your app creates objects and allocates memory for them. After some time the app frees some objects correctly but Windows memory manager doesn't deallocate freed memory at that time. Minimizing/restoring forces that process.

Regards, Geo
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Author Comment

by:bnz
ID: 6877195
Is there anything I can do to trim the memory usage

I tried to call
SetProcessWorkingSetSize( HInstance, $FFFFFFFF, $FFFFFFFF );

Read about it a delphi usergroup, but it didn't do the trick
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by:SteveWaite
ID: 6878878
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by:Madshi
ID: 6879153
>> SetProcessWorkingSetSize( HInstance, $FFFFFFFF, $FFFFFFFF );

Uah!!! Terrible!!! You've read THAT on a Delphi usergroup?

It has to look like this:

SetProcessWorkingSetSize(GetCurrentProcess, $FFFFFFFF, $FFFFFFFF );

HInstance is not a process handle, it is the module handle of the executable module, which is a *totally* different thing...

Regards, Madshi.
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Author Comment

by:bnz
ID: 6879234
I tried another thing. I created a new application with a button, it uses 1.7MB I call SetProcessWorkingSetSize (the correct way) and it drops to around 0.7MB and stays there no matter what I do. Why do Delphi reserve 1.7MB when 0.7MB seems to be enough.

Madshi:
hehe ehmm not quite, I read about SetProcessWorkingSetSize and filled hInstance in ...my self :)
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by:Madshi
ID: 6879325
Don't know what Delphi does there and why. Does SetProcessWorkingSetSize solve the problem with your original application, too?
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Author Comment

by:bnz
ID: 6879327
Yes it seems so
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by:Madshi
ID: 6879342
Fine! Please don't ask me to explain it - I can't...   :-/
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Author Comment

by:bnz
ID: 6879433
hehe, so your knowledge isn't inexhaustible after all ;)
I almost thought so
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by:Madshi
ID: 6879449
:-)
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Accepted Solution

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Wim ten Brink earned 300 total points
ID: 6896606
Delphi is just allocating 1 MB of memory for it's internal heap, I guess. This heap is used every time you create a new object. Since it's in RAM the creation of objects is pretty fast.
Once you call SetProcessWorkingSetSize this allocated memory is send to the swapfile and as long as you don't create new objects or use getmem-related commands to allocate more memory the reserved memory that's on the swap-file isn't required. But once you start allocating memory again, Delphi has to get the reserved memory from the swapfile which is a bit slower than allocating it directly.
Don't forget, within Windows memory manager Delphi uses it's own memory manager to allocate big chunks of data and to divide it in very small parts.
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