03/02/10

Process
  - a program in execution
  - note the creation time

Multiprocessing
  - multiple processes
  - each with own code, data and PCB
  - context switch (has a cost)

Multithreading
  - thread of control is a path of execution through a program
  - in multithreading, a process has multiple points of
    execution
  - threads have a "shared address space"

Process-only servers
  - each request handled by a separate process
  - two alternative approaches
    1. create a new process to handle a new request
      (i.e. a parent process forks child processes);
      delete the process when you've done
    2. on startup, create a pool of processes
      (preforking)
      new requests are assigned to an idle process;
      when you've done, don't delete the process;
      (might kill them after they've handled a certain
      number of requests, to avoid probs with, e.g.,
      memory leaks)

Thread-only servers
  - each request handled by a separate thread within a 
    single process

Hybrid servers
  - several processes each with several threads