[SOLVED] Real Time Threading under Linux (Debian)
lazarus / 32-Linux

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Greg · 2013-02-18 10:14

Hi!

I've built a daemon which spawns up to 32 threads.
This part is ok, everything thing runs smoothly.
Now i'd like to make these threads realtime threads as they are time
critical and mustn't be delayed.

I've tried many things but none seems to work (i check with htop / top
to see the priority and GetThreadPriority on each of these thread
inside the main thread).

Code: [Select]procedure TMyThread.Create( ); override
begin
      inherited Create( True );
      /* .. some initialization stuff ..  */
      priority := tpTimeCritical;
      ThreadSetPriority( GetCurrentThreadId, 15);
      resume;
end;

Looking back at the thread in top/htop the thread stayed at priority
20.
Trying ThreadSetPriority( GetCurrentThreadId, 15) always returns false
(i'm root).

What am i doing wrong ? Is top/htop the right place to see this
information ?

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Greg · 2013-02-18 15:34

ok. found out this : http://bugs.freepascal.org/view.php?id=16785

Thread priority is not supported on Linux....

I was wondering if anyone tried pthread_getschedparam /
pthread_setschedparam ?

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garlar27 · 2013-02-18 19:14

I never needed to set the thread's priority level. Never the less they
normally if I don't use a WaitToEvent the threads eat resources like
there's no tomorrow (like someone said in this forum).

Your threads do not respond as quick as you need, or you just want all
what system can give?

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Greg · 2013-02-19 07:49

Hi Garlar,

The app needs to treat in realtime multicast udp packet. I have to be
sure that this app has always the priority over other processes (like
a http server).
It's expected that the CPU will run at 80% consistently (a huge udp
bandwidth is used).

I tried to use daemon-start-stop parameters to set to realtime the
processus, but threads build don't inherit these parameters. :/

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Greg · 2013-02-19 08:28

ok. I found this http://www.mail-archive.com/fpc-
devel@lists.freepascal.org/msg17552.html.

Code: [Select]
uses  cthreads, unixtype, pthreads;

...
type
   TClassPriority = (cprOther, cprFIFO, cprRR);

...

function SetThreadPriority( aThreadID : TThreadID; class_priority :
TClassPriority; sched_priority: Integer ) : Boolean;
var
   param : sched_param;
   ret : Integer;
   aPriority : integer;
begin
     // 0-99
     param.sched_priority:= sched_priority;
     aPriority := Ord(class_priority);
     ret := pthread_setschedparam( pthread_t(aThreadID), aPriority,
@param);
     result := (ret = 0);
end;

It's working well!.

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bonmario · 2015-09-23 17:24

On my Ubuntu 15.04 64 it don't works.
With cprOther, i have the error 22
Code: [Select]EINVAL      = 22;   { Invalid argument }
With cprFIFO and with cprRR, i have error 1:
Code: [Select]EPERM       = 1;    { Operation not permitted }
Hi, Mario