[Python-checkins] r76202 - in python/branches/py3k/Doc: library/sys.rst whatsnew/3.2.rst

Wed Nov 11 00:18:31 CET 2009

Author: antoine.pitrou
Date: Wed Nov 11 00:18:31 2009
New Revision: 76202
Log:
Add a couple of words about the new GIL implementation
Modified:
 python/branches/py3k/Doc/library/sys.rst
 python/branches/py3k/Doc/whatsnew/3.2.rst
Modified: python/branches/py3k/Doc/library/sys.rst
==============================================================================

--- python/branches/py3k/Doc/library/sys.rst	(original)
+++ python/branches/py3k/Doc/library/sys.rst	Wed Nov 11 00:18:31 2009
@@ -282,6 +282,9 @@
 
 Return the interpreter's "check interval"; see :func:`setcheckinterval`.
 
+ .. deprecated:: 3.2
+ Use :func:`getswitchinterval` instead.
+
 
 .. function:: getdefaultencoding()
 
@@ -345,6 +348,12 @@
 collector.
 
 
+.. function:: getswitchinterval()
+
+ Return the interpreter's "thread switch interval"; see
+ :func:`setswitchinterval`.
+
+
 .. function:: _getframe([depth])
 
 Return a frame object from the call stack. If optional integer *depth* is
@@ -626,6 +635,11 @@
 performance for programs using threads. Setting it to a value ``<=`` 0 checks
 every virtual instruction, maximizing responsiveness as well as overhead.
 
+ .. deprecated:: 3.2
+ This function doesn't have an effect anymore, as the internal logic
+ for thread switching and asynchronous tasks has been rewritten.
+ Use :func:`setswitchinterval` instead.
+
 
 .. function:: setdefaultencoding(name)
 
@@ -689,6 +703,17 @@
 limit can lead to a crash.
 
 
+.. function:: setswitchinterval(interval)
+
+ Set the interpreter's thread switch interval (in seconds). This floating-point
+ value determines the ideal duration of the "timeslices" allocated to
+ concurrently running Python threads. Please note that the actual value
+ can be higher, especially if long-running internal functions or methods
+ are used. Also, which thread becomes scheduled at the end of the interval
+ is the operating system's decision. The interpreter doesn't have its
+ own scheduler.
+
+
 .. function:: settrace(tracefunc)
 
 .. index::
Modified: python/branches/py3k/Doc/whatsnew/3.2.rst
==============================================================================
--- python/branches/py3k/Doc/whatsnew/3.2.rst	(original)
+++ python/branches/py3k/Doc/whatsnew/3.2.rst	Wed Nov 11 00:18:31 2009
@@ -85,6 +85,27 @@
 (Contributed by Georg Brandl and Mattias Brändström;
 `appspot issue 53094 <http://codereview.appspot.com/53094>`_.)
 
+Multi-threading
+===============
+
+* The mechanism for serializing execution of concurrently running Python
+ threads (generally known as the GIL or Global Interpreter Lock) has been
+ rewritten. Among the objectives were more predictable switching intervals
+ and reduced overhead due to lock contention and the number of ensuing
+ system calls. The notion of a "check interval" to allow thread switches
+ has been abandoned and replaced by an absolute duration expressed in
+ seconds. This parameter is tunable through :func:`sys.setswitchinterval()`.
+ It currently defaults to 5 milliseconds.
+
+ Additional details about the implementation can be read from a `python-dev
+ mailing-list message
+ <http://mail.python.org/pipermail/python-dev/2009-October/093321.html>`_
+ (however, "priority requests" as exposed in this message have not been
+ kept for inclusion).
+
+ (Contributed by Antoine Pitrou)
+
+
 Optimizations
 =============
 
