High CPU usage in Linux Daemon (using TDaemon)
lazarus / 5-Lazarus Extra Components

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jl · 2009-07-14 08:37

I created a very simple Daemon and discovered that it takes up up to
half the CPU resources when doing nothing.  The problem does not occur
in win32.

I've attached the source and screen capture, simpledaemon-
screenshot.JPG.

Is there a command to make the daemon go to a sleeping or idle mode?

Appreciate any pointers.

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Loesje · 2009-07-14 20:54

It's a bug in fpPause. For some reason it returns immediately. But
that should be no problem for you. Your service should not exit the
OnExecute  procedure, until the service is terminated. Now your code
is terminated but the system doesn't know that so it waits forever....

ie:
procedure TDaemon1.DataModuleExecute(Sender: TCustomDaemon);
begin
  while status=csrunning do
    begin
    sleep(50);
    end;
end;

btw: using 'writeln' in a daemon is not a good idea. Maybe that
Application.Logger.debug('sometext'); is better.

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jl · 2009-07-15 09:37

Quote from: Loesje on July 14, 2009, 10:54:28 pmIt's a bug in fpPause.
For some reason it returns immediately. But that should be no problem
for you. Your service should not exit the OnExecute  procedure, until
the service is terminated. Now your code is terminated but the system
doesn't know that so it waits forever....

ie:
procedure TDaemon1.DataModuleExecute(Sender: TCustomDaemon);
begin
  while status=csrunning do
    begin
    sleep(50);
    end;
end;

btw: using 'writeln' in a daemon is not a good idea. Maybe that
Application.Logger.debug('sometext'); is better.


Thanks, this worked perfect.  I just discovered that the Ubuntu
version of Application.Logger rocks - the viewer scrolls real-time!

By the way, I noticed that the daemon waiting channel is always at
'futex_wait' while the majority of the rest like Gnome-panel are at
'do_poll'.  Is that suppose to be correct?

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jl · 2009-08-07 04:25

Thanks.  By the way, I found out that if I don't use
TDaemon1.DataModuleExecute, I won't have this problem in the first
place.  I've moved the startup code to TDaemon1.DataModuleStart.

Meanwhile, I'm facing a new problem.  I'm not able to quit a service
startup (both Win32 and Linux) - I want to do that if say the UDP port
is occupied when starting my UDP Server:

Code: [Select]procedure TDaemon1.DataModuleStart(Sender:
TCustomDaemon; var OK: boolean);

 while IdUDPServer1.Active = False do
  begin
    try
      IdUDPServer1.Active := True;          //binding
        ..............
    except
      on E: Exception do
      begin
        writelog('error','Main', E.ClassName + #9 +
          'Errors raised when starting server with message :' +
E.message);
        writelog('error','Main','Encountered fatal error.
 Exiting.');;
        sleep(5000);
     //     OK:=false;
    //  exit;
      end;
    end;
  end;    
The following code was added but the service will become hang - not
started and not stopped, even after 5 minutes.  I have to kill it from
the process, so this is no go.  

     //     OK:=false;
    //  exit;