Delphi - Minimize & Restore frees up memory ?

Question

Hello All,

I have been a dabbling into delphi off and on for years and I have always wondered why does minimizing and restoring an application cause it to use less memory ?

As an example I am using delphi 7 and I create a new project with nothing on it but the blank form all projects start out with and then I press F9 to run the application and then look at the memory usage for the app and it's sitting at around 3.5mb I then minimize the app and the memory usage goes down to around 760kb and then I finally restore the app and the memory usage goes back up to around 1.5mb which is roughly 1/2 of what it was when it first loaded and this has always confused me as to what is making this happen and even more to the point is there anyway to start the application with some directive that makes it use the 1.5mb of memory instead of the 3.5mb it normally uses.

Cheers, Dave

Answer 1

probably is something with windows memory management. try the same thing with the windows calculator and the behavior is the same :))

here an answer: http://support.microsoft.com/?kbid=293215 and some folks have the same question: http://digital.ni.com/public.nsf/allkb/9EA3D4258E037B8A8625763300434D4D

best regards,

Answer 2

Here you can find a very clear explanation from Ian Martins. When the application minimizes the system call SetProcessWorkingSetSize procedure for free inactive memory of process.

You can do the same adding this code to your application. In a button OnClick you can do this:

procedure LiberarMemoria;
begin
  if Win32Platform = VER_PLATFORM_WIN32_NT then
    SetProcessWorkingSetSize(GetCurrentProcess, $FFFFFFFF, $FFFFFFFF);
end;

The effect is similar to minimize the application. If your application do some task thah eventually use a big block of memory, you can force it to free after use it, using this small code.

Regards

Answer 3

See Barry Kelly's answer on this question.