[pypy-commit] extradoc extradoc: Draft.

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: extradoc
Changeset: r4212:26d6c3ac0f6e
Date: 2012-06-10 19:09 +0200
http://bitbucket.org/pypy/extradoc/changeset/26d6c3ac0f6e/

Log:	Draft.

diff --git a/blog/draft/stm-jun2012.rst b/blog/draft/stm-jun2012.rst
new file mode 100644
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+STM with threads
+================
+
+Hi all,
+
+A quick update.  The first version of pypy-stm `based on regular
+threads`_ is ready.  Still having no JIT and a 4-or-5-times performance
+hit, it is not particularly fast, but I am happy that it turns out not
+to be much slower than the previous thread-less attempts.  It is at
+least fast enough to run faster (in real time) than an equivalent no-STM
+PyPy, if fed with an eight-threaded program on an eight-core machine
+(provided, of course, you don't mind it eating all 8 cores' CPU power
+instead of just one :-).
+
+You can download and play around with `this binary`_ for Linux 64.  It
+was made from the `stm-thread`_ branch of the PyPy repository.  (Be sure
+to put it where it can find its stdlib, e.g. by putting it inside the
+directory from the official `1.9 release`_.)  
+
+This binary supports the ``thread`` module and runs without the GIL.
+So, despite the factor-of-4 slow-down issue, it should be the *fourth*
+complete Python interpreter in which we can reasonably claim to have
+resolved the problem of the GIL.  (The first one was Greg Stein's Python
+1.4, re-explored here_; the second one is Jython_; the third one is
+IronPython_.)  Unlike the previous three, it is also the first one to
+offer full GIL semantics to the programmer, and additionally
+``thread.atomic`` (see below).  (As a side note, the specifications of
+Intel's TSX_ are public, so there is of course at least one team that
+tries to get the same result with future Hardware Transactional Memory.
+I am not allowed to go into any more details, which makes little sense
+if you ask me, but there you go.)
+
+The binary I linked to above supports all built-in modules from PyPy,
+apart from ``signal``, still being worked on (which can be a bit
+annoying because standard library modules like ``subprocess`` depend on
+it).  The ``sys.get/setcheckinterval()`` functions can be used to tweak
+the frequency of the automatic commits.  Additionally, it offers
+``thread.atomic``, described in the `previous blog post`_ as a way to
+create longer atomic sections (with the observable effect of preventing
+the "GIL" to be released during that time).  A complete
+``transaction.py`` module based on it is available `from the sources`_.
+
+The main missing features are:
+  
+- the ``signal`` module;
+
+- the Garbage Collector, which does not do major collections so far, only
+  minor ones;
+
+- and finally, the JIT, which needs some amount of integration to generate
+  the correctly-tweaked assembler.
+
+Have fun!
+
+
+Armin.
+
+
+.. _`based on regular threads`: http://morepypy.blogspot.ch/2012/05/stm-update-back-to-threads.html
+.. _`previous blog post`: http://morepypy.blogspot.ch/2012/05/stm-update-back-to-threads.html
+.. _`this binary`: http://cobra.cs.uni-duesseldorf.de/~buildmaster/misc/pypy-stm-38eb1fbc3c8d.bz2
+.. _`1.9 release`: https://bitbucket.org/pypy/pypy/downloads/pypy-1.9-linux64.tar.bz2
+.. _`stm-thread`: https://bitbucket.org/pypy/pypy/src/stm-thread
+.. _`from the sources`: https://bitbucket.org/pypy/pypy/src/stm-thread/lib_pypy/transaction.py
+.. _`since long ago`: http://dabeaz.blogspot.ch/2011/08/inside-look-at-gil-removal-patch-of.html
+.. _here: http://dabeaz.blogspot.ch/2011/08/inside-look-at-gil-removal-patch-of.html
+.. _Jython: http://jython.org/
+.. _IronPython: http://ironpython.net/
+.. _TSX: http://software.intel.com/en-us/blogs/2012/02/07/transactional-synchronization-in-haswell/