From: d@d.d   
      
   Hello..   
      
      
   And about Message Passing Process Communication Model and Shared Memory   
   Process Communication Model:   
      
   An advantage of shared memory model is that memory communication is   
   faster as compared to the message passing model on the same machine.   
      
   Read the following to notice it:   
      
   Why did Windows NT move away from the microkernel?   
      
   "The main reason that Windows NT became a hybrid kernel is speed. A   
   microkernel-based system puts only the bare minimum system components in   
   the kernel and runs the rest of them as user mode processes, known as   
   servers. A form of inter-process communication (IPC), usually message   
   passing, is used for communication between servers and the kernel.   
      
   Microkernel-based systems are more stable than others; if a server   
   crashes, it can be restarted without affecting the entire system, which   
   couldn't be done if every system component was part of the kernel.   
   However, because of the overhead incurred by IPC and context-switching,   
   microkernels are slower than traditional kernels. Due to the performance   
   costs of a microkernel, Microsoft decided to keep the structure of a   
   microkernel, but run the system components in kernel space. Starting in   
   Windows Vista, some drivers are also run in user mode."   
      
      
   More about message passing..   
      
   "One problem that plagues microkernel implementations is relatively poor   
   performance. The message-passing layer that connects   
   different operating system components introduces an extra layer of   
   machine instructions. The machine instruction overhead introduced   
   by the message-passing subsystem manifests itself as additional   
   execution time. In a monolithic system, if a kernel component needs   
   to talk to another component, it can make direct function calls   
   instead of going through a third party."   
      
   However, shared memory model may create problems such as synchronization   
   and memory protection that need to be addressed.   
      
   Message passing’s major flaw is the inversion of control–it is a moral   
   equivalent of gotos in un-structured programming (it’s about time   
   somebody said that message passing is considered harmful).   
      
   Also some research shows that the total effort to write an MPI   
   application is significantly higher than that required to write a   
   shared-memory version of it.   
      
      
      
   Thank you,   
   Amine Moulay Ramdane.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)