Re: Ada and linux real time

[slos <new.stephane.los@gmail.com>]

I am learning Ada, don't laugh please ! ;-)

Here is mine :

with System;
with Ada.Text_IO; use Ada.Text_IO;
with Ada.Real_Time; use Ada.Real_Time;

procedure RT_test is

   procedure cyclic is
      real1 : Float := 10.0;
      real2 : Float := 20.0;
      real3 : Float :=  0.0;
   begin
      for Index in 0 .. 1000000 loop -- should do something useful
instead
         real3 := real1 * real2;
      end loop;
   end cyclic;

   task type Periodic_Task
     (Task_Priority           : System.Priority;
      Period_In_Milliseconds  : Natural) is
      pragma Priority (Task_Priority);
   end Periodic_Task;

   task body Periodic_Task is
      Next_Time  : Ada.Real_Time.Time := Clock;
      MyPeriod   : constant Time_Span := Milliseconds
(Period_In_Milliseconds);
      Max_Times  : Integer := 10000 / Period_In_Milliseconds; -- we
want the test to run 10 s
      Times      : Integer := 0;
      Stats      : array (1 .. 10) of Integer;
      Thresholds : array (1 .. 10) of Duration;
      MyDuration       : Duration;
      MyMinDuration    : Duration;
      MyMaxDuration    : Duration;
      MyPeriodDuration : Duration := To_Duration (MyPeriod);
   begin
      Put_Line ("MyPeriod_Duration    : " & Duration'Image
(MyPeriodDuration));

      for Index in Stats'Range loop
         Stats (Index) := 0;
      end loop;

      Thresholds( 1) := MyPeriodDuration *  0.001;
      Thresholds( 2) := MyPeriodDuration *  0.005;
      Thresholds( 3) := MyPeriodDuration *  0.010;
      Thresholds( 4) := MyPeriodDuration *  0.050;
      Thresholds( 5) := MyPeriodDuration *  0.100;
      Thresholds( 6) := MyPeriodDuration *  0.500;
      Thresholds( 7) := MyPeriodDuration *  1.000;
      Thresholds( 8) := MyPeriodDuration *  5.000;
      Thresholds( 9) := MyPeriodDuration * 10.000;
      Thresholds(10) := MyPeriodDuration * 20.000;
      loop
         Next_Time := Next_Time + MyPeriod;

         cyclic; -- Do something useful

         delay until Next_Time;

         MyDuration := To_Duration (Clock - Next_Time);
         if (Times = 0) then
            MyMinDuration := MyDuration;
            MyMaxDuration := MyDuration;
         else
            if MyMinDuration > MyDuration then
               MyMinDuration := MyDuration;
            else if MyMaxDuration < MyDuration then
                  MyMaxDuration := MyDuration;
               end if;
            end if;
         end if;

         for Index in Stats'Range loop
            if MyDuration < Thresholds (Index) then
               Stats (Index) := Stats (Index) + 1;
               exit;
            end if;
         end loop;

         Times := Times + 1;

         exit when Times > Max_Times;

      end loop;
      Put_Line ("Et Hop ! Times : " & Times'Img & " Duration Min : " &
Duration'Image (MyMinDuration) & " Max : " & Duration'Image
(MyMaxDuration));
      for Index in Stats'Range loop
         Put_Line (Integer'Image(Index) & " | Thresholds := " &
Duration'Image(Thresholds(Index)) & " | Stats := " &
Integer'Image(Stats(Index)));
      end loop;
      Put_Line ("Periodic_Task finished !");
   end Periodic_Task;

   My_Periodic_Task : Periodic_Task (Task_Priority          => 97,
                                     Period_In_Milliseconds => 10);
begin
   Put_Line ("Real Time test...");

end RT_test;

And the results don't tell me anything...
I have to think about putting some load on the system.

The test run for 10 s and outputs the difference between expected
sleep duration and actual, sorting the results in an array.

With no load either and no RT kernel :

Linux debian-sid 3.2.0-2-amd64 #1 SMP Tue Mar 13 16:54:04 UTC 2012
x86_64 GNU/Linux

/home/slos/Ada/NPLC/build/rt_test
Real Time test...
MyPeriod_Duration    :  0.010000000
Et Hop ! Times :  1001 Duration Min :  0.000042000 Max :  0.000276000
 1 | Thresholds :=  0.000010000 | Stats :=  0
 2 | Thresholds :=  0.000050000 | Stats :=  1
 3 | Thresholds :=  0.000100000 | Stats :=  560
 4 | Thresholds :=  0.000500000 | Stats :=  440
 5 | Thresholds :=  0.001000000 | Stats :=  0
 6 | Thresholds :=  0.005000000 | Stats :=  0
 7 | Thresholds :=  0.010000000 | Stats :=  0
 8 | Thresholds :=  0.050000000 | Stats :=  0
 9 | Thresholds :=  0.100000000 | Stats :=  0
 10 | Thresholds :=  0.200000000 | Stats :=  0
Periodic_Task finished !
[2012-03-18 22:39:45] process terminated successfully (elapsed time:
10.12s)