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1990-10-30
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OPSTACK - Unit for Monitoring Heap and Stack Usage
-------------------------------------------------------
Brian Foley
TurboPower Software
11/90
Version 1.1
Released to the public domain
Overview
------------------------------------------------------------------------------
OPSTACK allows you to accurately monitor a program's stack and heap usage
simply by adding OPSTACK to the beginning of the program's USES list. The
following program demonstrates how to use it:
program OpStackTest;
{-Simple program to test OpStack}
uses
OpStack, Crt;
var
P : Pointer;
procedure StackEater;
{-Use some stack space}
var
BigArray : array[1..12331] of Byte; {this is on the stack}
begin
{delay a moment to insure that OpStack sees what we've used}
Delay(10);
end;
begin
{use some stack and heap space}
GetMem(P, 56789);
StackEater;
end.
If you run this little demo program, you'll see that OpStack automatically
displays the amount of heap and stack space used by the program when it ends.
In addition, it also shows the greatest amount of space used on the free list
at any one time (under Turbo Pascal 4.0-5.5), and an estimate of the total
amount of memory actually used by the program (for code, data, stack, and
heap). This last value includes any unused memory set aside for the stack
segment. It does not include the amount of space used for the free list (if
any), nor does it include any heap space allocated for an overlay buffer.
Normally it is just this easy. In some cases, however, you may want or need to
handle the reporting of results yourself. If so, you would set
ReportStackUsage to False and call CalcStackUsage to obtain the necessary
information.
If you want to disable stack monitoring temporarily--when executing other
programs, for example--you can call RestoreInt8 to disable it and InstallInt8
to reenable it.
OpStack can monitor only a single stack segment, normally the one in use when
the program began. If you need to use it in a program that uses an alternate
stack (a memory resident program, perhaps), you'll have to initialize three
global variables before the first time that you switch to that stack. Here's
an example:
{disable OpStack momentarily}
RestoreInt8;
{OurSS has the stack segment to watch}
OurSS := AlternateStackSegment;
{InitialSP has the value of "SP" when the program began}
InitialSP := TopOfAlternateStack;
{LowestSP has the lowest value of SP so far, same as InitialSP at first}
LowestSP := InitialSP;
{reactivate OpStack}
InstallInt8;
Finally, in order to improve the accuracy of its results, OpStack reprograms
the timer chip so that it can get control of the machine over 1000 times a
second. For this reason, OpStack should not be used in programs that
themselves reprogram the chip, or in programs that are using the PEP unit in
Turbo Analyst. If you wish to change the rate at which samples are taken, you
can call the SetSampleRate routine:
{select 100 samples per second}
SetSampleRate(100);
The minimum value allowed is 18 samples per second, which is what the rate
would be OpStack didn't reprogram the timer.