Tuesday, February 12, 2008

TDM#5: Slimming the Fat off Your Apps

I think that the best TDM article title I've had is Slimming the Fat off Your Apps. It was published in November 1998 and we're still in the Delphi 4 era (but as always many people were still using the older versions, D2 and D3).

The article intro said:

"Hallvard Vassbotn wants to slim the fat off your software: tune in here if you want [your programs] to be leaner and fitter..."

The core points of the article are:

  • The Windows NT family of operating systems reduce the apparent memory footprint of an application when you minimize it
  • The code for compiler-generated  initialization and finalization sections of units changed between D2 and D3 (to the better and worse)
  • The mechanism and code for invoking initialization and finalization sections changed markedly between D2 and D3
  • Initialization code is spread out through the EXE file - causing "heavy" memory usage after startup.
  • There is a trick to simulate the minimize-app memory "savings" in code (calling SetProcessWorkingSetSize)

In my opinion, the whole memory savings issue is a game of smoke and mirrors - no actual memory is saved, just the internal accounting and how pages are marked as belonging to an applications working set or not is affected. It may impress users looking at the mostly misleading memory usage in Task Manager, but it has no effect on the real memory pressure of the machine.

Here is the code (courtesy of Ray Nelson) for trimming the "fat":

unit TrimMem;
// Code courtesy of Roy Nelson (rnelson@inprise.com),
// Inprise European Professional Support
// Call TrimWorkingSet from you project file or from a package
// to reduce the memory overhead - note that this will only work
// on Windows NT.
// From Delphi Magazine article "Slimming the fat off your Apps"
// by Hallvard Vassbotn, hallvard@falcon.no

procedure TrimWorkingSet;



procedure TrimWorkingSet;
MainHandle : THandle;
MainHandle := OpenProcess(PROCESS_ALL_ACCESS, false, GetCurrentProcessID);


The full PDF article and code are available for download.

Copyright © 2004-2007 by Hallvard Vassbotn