[pypy-commit] pypy default: Document branch

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: 
Changeset: r72235:c76af9b7eea9
Date: 2014-06-25 21:35 +0200
http://bitbucket.org/pypy/pypy/changeset/c76af9b7eea9/

Log:	Document branch

diff --git a/pypy/doc/whatsnew-head.rst b/pypy/doc/whatsnew-head.rst
--- a/pypy/doc/whatsnew-head.rst
+++ b/pypy/doc/whatsnew-head.rst
@@ -30,3 +30,12 @@
 x86-64, the JIT backend has a special optimization that lets it emit
 directly a single MOV from a %gs- or %fs-based address. It seems
 actually to give a good boost in performance.
+
+.. branch: fast-gil
+A faster way to handle the GIL, particularly in JIT code. The GIL is
+now a composite of two concepts: a global number (it's just set from
+1 to 0 and back around CALL_RELEASE_GIL), and a real mutex. If there
+are threads waiting to acquire the GIL, one of them is actively
+checking the global number every 0.1 ms to 1 ms.  Overall, JIT loops
+full of external function calls now run a bit faster (if no thread was
+started yet), or a *lot* faster (if threads were started already).