1. concurrency - what is it

   1. more than one computation being carried out at the same time

   2. coordination among the concurrent computations - none is trivial concurrency (although providing trivial concurrency is non-trivial)

2. concepts

   1. process - the computation

   2. execution threads - the action

   3. shared resources - inter-computation; intra-computation; explicitly shared resources

   4. real vs virtual concurrency - don't exploit concurrency features; stick to the standards

   5. relations among computations - execution relations; sharing relations

   6. context switching - overhead particularly

3. concurrency and networking

   1. networking is a naturally concurrent environment - lots of hosts attached

   2. client concurrency is effortless; server concurrency is not

4. concurrency apis

   1. fork() - create an exact (almost) copy of the calling computation

      1. the fork() return value - pid

      2. if ((pid = fork())) { /* in parent */ } else { /* in child */ }

      3. what else - threads; solaris duplicates threads in the child

   2. exec() and friends

      1. gut and refinish the calling computation - run a new computation

      2. the friends differ in the arguments passed and how they're passed

      3. a successful call doesn't return

5. io operations

   1. most io operations are blocking - cuts down on concurrency

   2. asynchronous io operations - polling operations

   3. thread safe io operations

   4. multiplexing operations - virtual concurrency

This page last modified on 13 February 2001.