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From: Michael Erdmann <michael.erdmann@snafu.de>
Subject: Q: Binding tasks to CPU's seems not to work with Task_Info pragma?!
Newsgroups: comp.lang.ada
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Date: 10 Aug 2013 17:56:44 GMT
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Date: 2013-08-10T19:56:44+02:00
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Hallo,

i am trying to bind my task to specific processors using gnat packages. 

      function CPU( i : Positive ) return Task_Info.Task_Info_Type is
         T : Task_Info.Task_Info_Type := new Thread_Attributes;
      begin
         T.CPU_Affinity.bits := (others => false );
         T.CPU_Affinity.bits(i) :=true;
         return T;
      end;
      
      task type Task_Type( id : Natural ) is
         Pragma Priority(4);
         Pragma Task_Info(CPU(Id));
      end Task_Type;

      TT : array(1..Nbr_Of_Threads) of Task_Access; 
   begin
      for i in TT'Range loop
         TT(i) := new Task_Type(i);
      end loop;
      ....

Assume Nbr_Of_Threads = 4; i get on my linux box (OpenSuse 12.3) the following
top results. 


top - 19:40:02 up 31 min,  2 users,  load average: 1.77, 0.46, 0.19
Tasks: 200 total,   1 running, 199 sleeping,   0 stopped,   0 zombie
Cpu0  :  0.3%us,  0.0%sy,  0.0%ni, 99.7%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu1  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu2  :100.0%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu3  :100.0%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu4  :100.0%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu5  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu6  :100.0%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu7  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   3981796k total,   669496k used,  3312300k free,      856k buffers
Swap: 10482408k total,        0k used, 10482408k free,   340328k cached

I would have expected CPU 0..3 being busy. Even worse the next time i start 
my program the cpu's are assigned differently :-/

I am a bit frustrated because i can do the trick with taskset without any 
major effort. Any idea what i am doing wrong? 

The complete source should be avaiable here: https://gist.github.com/merdmann/6201405

I am using:
gcc version 4.5.4 20120510 for GNAT GPL 2012 (20120509) (GCC) 
Linux hal 3.1.10-1.29-xen #1 SMP Fri May 31 20:10:04 UTC 2013 (2529847) x86_64 x86_64 x86_64 GNU/Linux


Thanx in advance
    Michael