Author: allison
Date: Wed Dec 27 22:31:09 2006
New Revision: 16281

Modified:
   trunk/docs/pdds/clip/pdd25_concurrency.pod

Log:
[pdd]: Adding notes on concurrency scheduler and core definitions.


Modified: trunk/docs/pdds/clip/pdd25_concurrency.pod
==============================================================================
--- trunk/docs/pdds/clip/pdd25_concurrency.pod  (original)
+++ trunk/docs/pdds/clip/pdd25_concurrency.pod  Wed Dec 27 22:31:09 2006
@@ -16,10 +16,35 @@
 
 =head1 DEFINITIONS
 
-Concurrency
+I<Concurrency> is a parallel execution of units of code (on
+multiprocessor machines), or a flexible ordering of units of code (on
+single processor machines). For certain problem spaces, concurrency
+offers significant speed gains by parceling out processor-intensive
+activity or by ensuring that a wait for input or system resources
+doesn't hold up the entire application.
+
+A I<Task> is a unit of code that can be executed in parallel.
 
 =head1 DESCRIPTION
 
+=over 4
+
+=item - Parrot supports multiple concurrency models, including POSIX
+threads, event-based programming, and asynchronous I/O.
+
+=item - To reduce conflicts between concurrency models, Parrot provides
+a single central concurrency scheduler for each interpreter instance.
+Each concurrency model defines a Task PMC that supports a standard
+minimal interface. The scheduler can interact with tasks from various
+models without direct access to the details of each model.
+
+=item - On multiprocessor systems, the scheduler is responsible for
+allocating tasks to processors, or for delegating that allocation to the
+underlying OS.
+
+
+=back
+
 =head1 DEFINITIONS
 
 So we can all talk about things the same way, the following

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