Re: Orbit Performance Questions

[Michael Meeks <michael ximian com>]

Hi Anil,

On Fri, 2001-12-28 at 13:54, anil kumar wrote:
>   I am new to ORBIT and CORBA,  right now i am looking at the 
>   performance of ORBIT  so that i can use it for  Real Time
>   Software Development. We are also planning to  put 
>   ORB code into Linux Kernel also if some performance issues 
>   come(So we need Open Source ORB ).Some ORB i have found 
>   from  Internet are ORBIT,MICO,TAO.

	Sure.

>        I have some  basic doubt how   communication takes 
>   place when the client and server both are running on the same 
>   machine.

	Well - that is moderately pluggable ;-) if you have some brilliant plan
for how to do this, it should be easy to plug a new approach in - after
all in Kernel land you have more possibilities.

	Essentialy there are two approaches - if we are in-proccess we invoke
the C method via a direct function pointer cast from the vtable - if it
is non NULL doh - I'll just paste the stub. This is all for ORBit2 BTW.
ORBit1 uses a somewhat more bloated and to my mind inferior approach.


Bonobo_Canvas_ArtUTA *
Bonobo_Canvas_Component_update(Bonobo_Canvas_Component _obj,
			       const Bonobo_Canvas_State * state,
			       const Bonobo_Canvas_affine aff,
			       const Bonobo_Canvas_SVP * clip_path,
			       const CORBA_long flags, CORBA_double * x1,
			       CORBA_double * y1, CORBA_double * x2,
			       CORBA_double * y2, CORBA_Environment * ev)
{
   Bonobo_Canvas_ArtUTA *_ORBIT_retval;

#ifndef ORBIT_STUB_DEBUG_LOCAL
   if (ORBIT_STUB_IsBypass(_obj, Bonobo_Canvas_Component__classid)) {
      ORBIT_STUB_PreCall(_obj);
      _ORBIT_retval =
	 ((POA_Bonobo_Canvas_Component__epv *)
	  ORBIT_STUB_GetEpv(_obj,
			    Bonobo_Canvas_Component__classid))->
	 update(ORBIT_STUB_GetServant(_obj), state, aff, clip_path, flags, x1,
		y1, x2, y2, ev);
      ORBIT_STUB_PostCall(_obj);
   } else
#endif	/* ORBIT_STUB_DEBUG_LOCAL */
   {				/* remote marshal */
      gpointer _args[] = {
	 (gpointer) state, (gpointer) aff, (gpointer) clip_path,
	    (gpointer) & flags, &x1, &y1, &x2, &y2
      };

      ORBit_small_invoke_stub(_obj,
			      &Bonobo_Canvas_Component__iinterface.methods.
			      _buffer[0], &_ORBIT_retval, _args, NULL, ev);

   }
   return _ORBIT_retval;
}

	So you see we can pass it straight off through the Entry Point Vector
(epv - a sort of vtable ) to the method - OR

	we push the args into a normalized form [ defined in
interface-indirection.gnumeric ] and call the generic
'ORBit_small_invoke_stub' method. If this is called in-proc then these
arguments [ in the standard form ] are passed to the pluggable 'Skel'
code for that object / interface. This is to allow trivial cross
language method invocation - you could plug a marshaler there for the
client side I think. Otherwise if it is out of proc the code genericaly
marshals the arguments to the Common Data Representation (CDR) AFAIR;
see orbit-small.c. 

>  a:  Whether the  data is converted  to the XDR format or not?

	XDR - no idea, it is always converted to IIOP in the remote case, the
in-proc case is rather different.

>  b:  What IPC mechanism ORBIT uses for communication?

	Fast Unix Domain Sockets on the same machine, otherwise we can use
IPv6/IPv4 sockets / IRDA etc. + SSL ( in theory ) so ... a number of IPC
mechanisms.

>  c:  How Communication takes place when the Client  and Server
>      both are running on different machine?

	as above really.

>  d:  Is Corba suited for Real Time Application or not?

	Possibly - with the new non-blocking code going into ORBit2 it might
become more suitable; it depends how hard your realtime requirements are
I suppose.

>      I am also interested in orbit source code so that 
>   if  some performance bottleneck is found then  optimisation 
>   of code can be done. So , please let me know from which point i 
>   should start  reading code.

	You should checkout the 'linc' and 'ORBit2' modules from Gnome CVS [
see http://developer.gnome.org for details ]. Most of the ORB can be
understood by a little reading of:

	orbit-small.c, corba-any.c, poa.c, corba-object.c all in
ORBit2/src/orb/orb-core & src/orb/poa.

>     If anyone of  you have some ORBs performance document then
>     please  send me the URL.

	Sadly not - we do however have a set of known optimizations that we
should make sometime - with the bincompat overhead to make them as
ORBit2 stabilizes.

	HTH,

		Michael.

-- 
 mmeeks@gnu.org  <><, Pseudo Engineer, itinerant idiot