...get the CPU usage in percent on Windows NT/2000/XP?

Author: Thomas Stutz

Homepage: http://www.swissdelphicenter.ch

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const

SystemBasicInformation = 0;

SystemPerformanceInformation = 2;

SystemTimeInformation = 3;

type

TPDWord = ^DWORD;

TSystem_Basic_Information = packed record

dwUnknown1: DWORD;

uKeMaximumIncrement: ULONG;

uPageSize: ULONG;

uMmNumberOfPhysicalPages: ULONG;

uMmLowestPhysicalPage: ULONG;

uMmHighestPhysicalPage: ULONG;

uAllocationGranularity: ULONG;

pLowestUserAddress: Pointer;

pMmHighestUserAddress: Pointer;

uKeActiveProcessors: ULONG;

bKeNumberProcessors: byte;

bUnknown2: byte;

wUnknown3: word;

end;

type

TSystem_Performance_Information = packed record

liIdleTime: LARGE_INTEGER; {LARGE_INTEGER}

dwSpare: array[0..75] of DWORD;

end;

type

TSystem_Time_Information = packed record

liKeBootTime: LARGE_INTEGER;

liKeSystemTime: LARGE_INTEGER;

liExpTimeZoneBias: LARGE_INTEGER;

uCurrentTimeZoneId: ULONG;

dwReserved: DWORD;

end;

var

NtQuerySystemInformation: function(infoClass: DWORD;

buffer: Pointer;

bufSize: DWORD;

returnSize: TPDword): DWORD; stdcall = nil;

liOldIdleTime: LARGE_INTEGER = ();

liOldSystemTime: LARGE_INTEGER = ();

function Li2Double(x: LARGE_INTEGER): Double;

begin

Result := x.HighPart * 4.294967296E9 + x.LowPart

end;

procedure GetCPUUsage;

var

SysBaseInfo: TSystem_Basic_Information;

SysPerfInfo: TSystem_Performance_Information;

SysTimeInfo: TSystem_Time_Information;

status: Longint; {long}

dbSystemTime: Double;

dbIdleTime: Double;

bLoopAborted : boolean;

begin

if @NtQuerySystemInformation = nil then

NtQuerySystemInformation := GetProcAddress(GetModuleHandle('ntdll.dll'),

'NtQuerySystemInformation');

// get number of processors in the system

status := NtQuerySystemInformation(SystemBasicInformation, @SysBaseInfo, SizeOf(SysBaseInfo), nil);

if status <> 0 then Exit;

// Show some information

with SysBaseInfo do

begin

ShowMessage(

Format('uKeMaximumIncrement: %d'#13'uPageSize: %d'#13+

'uMmNumberOfPhysicalPages: %d'+#13+'uMmLowestPhysicalPage: %d'+#13+

'uMmHighestPhysicalPage: %d'+#13+'uAllocationGranularity: %d'#13+

'uKeActiveProcessors: %d'#13'bKeNumberProcessors: %d',

[uKeMaximumIncrement, uPageSize, uMmNumberOfPhysicalPages,

uMmLowestPhysicalPage, uMmHighestPhysicalPage, uAllocationGranularity,

uKeActiveProcessors, bKeNumberProcessors]));

end;

bLoopAborted := False;

while not bLoopAborted do

begin

// get new system time

status := NtQuerySystemInformation(SystemTimeInformation, @SysTimeInfo, SizeOf(SysTimeInfo), 0);

if status <> 0 then Exit;

// get new CPU's idle time

status := NtQuerySystemInformation(SystemPerformanceInformation, @SysPerfInfo, SizeOf(SysPerfInfo), nil);

if status <> 0 then Exit;

// if it's a first call - skip it

if (liOldIdleTime.QuadPart <> 0) then

begin

// CurrentValue = NewValue - OldValue

dbIdleTime := Li2Double(SysPerfInfo.liIdleTime) - Li2Double(liOldIdleTime);

dbSystemTime := Li2Double(SysTimeInfo.liKeSystemTime) - Li2Double(liOldSystemTime);

// CurrentCpuIdle = IdleTime / SystemTime

dbIdleTime := dbIdleTime / dbSystemTime;

// CurrentCpuUsage% = 100 - (CurrentCpuIdle * 100) / NumberOfProcessors

dbIdleTime := 100.0 - dbIdleTime * 100.0 / SysBaseInfo.bKeNumberProcessors + 0.5;

// Show Percentage

Form1.Label1.Caption := FormatFloat('CPU Usage: 0.0 %',dbIdleTime);

Application.ProcessMessages;

// Abort if user pressed ESC or Application is terminated

bLoopAborted := (GetKeyState(VK_ESCAPE) and 128 = 128) or Application.Terminated;

end;

// store new CPU's idle and system time

liOldIdleTime := SysPerfInfo.liIdleTime;

liOldSystemTime := SysTimeInfo.liKeSystemTime;

// wait one second

Sleep(1000);

end;

end;

procedure TForm1.Button1Click(Sender: TObject);

begin

GetCPUUsage

end;

// See also AdCpuUsage (for 95/98/NT/2000/XP)