The correct method of TProcessInfo.PerSystem in Linux

[zen010101]

Here is my edition:

function TProcessInfo.PerSystem(out Idle, Kernel, User: single): boolean;
var
  P: PUtf8Char;
  U, K, I, S: cardinal;
  U2, K2, I2, S2: cardinal;
begin
  // see http://www.linuxhowtos.org/System/procstat.htm
  result := false;
  P := pointer(StringFromFile('/proc/stat', {nosize=}true));
  if P = nil then
    exit;
  // e.g. 'cpu  3418147 18140 265232 6783435 12184 0 34219 0 0 0'
  U := GetNextCardinal(P){=user} + GetNextCardinal(P){=nice};
  K := GetNextCardinal(P){=system};
  I := GetNextCardinal(P){=idle};
  S := U + K + I;
  result := S <> 0;
  if not result then
    exit;

  sleep(200);

  P := pointer(StringFromFile('/proc/stat', {nosize=}true));
  U2 := GetNextCardinal(P){=user} + GetNextCardinal(P){=nice};
  K2 := GetNextCardinal(P){=system};
  I2 := GetNextCardinal(P){=idle};
  S2 := U2 + K2 + I2;

  Kernel := {%H-}SimpleRoundTo2Digits(((K2-K) * 100) / (S2-S));
  User   := {%H-}SimpleRoundTo2Digits(((U2-U) * 100) / (S2-S));
  Idle   := 100 - Kernel - User; // ensure sum is always 100%
end; { TODO : use a diff approach for TProcessInfo.PerSystem on Linux? }

[synopse]

Using a Sleep() is not possible because it should be not blocking.