[pypy-commit] extradoc extradoc: Add my own comments in three places

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: extradoc
Changeset: r5468:d9be15557668
Date: 2014-11-17 14:10 +0100
http://bitbucket.org/pypy/extradoc/changeset/d9be15557668/

Log:	Add my own comments in three places

diff --git a/blog/draft/tornado-stm.rst b/blog/draft/tornado-stm.rst
--- a/blog/draft/tornado-stm.rst
+++ b/blog/draft/tornado-stm.rst
@@ -170,7 +170,7 @@
     File "/home/arigo/hg/pypy/stmgc-c7/lib-python/2.7/_weakrefset.py", line 70, in __contains__
     File "/home/arigo/hg/pypy/stmgc-c7/lib-python/2.7/_weakrefset.py", line 70, in __contains__
 
-**FIXME** why does it happen?
+[Armin: It is unclear why this happens so far.  We'll investigate...]
 
 The second conflict (without etag tweaks) originates
 in the transaction module, from this piece of code::
@@ -180,7 +180,9 @@
                     got_exception)
         counter[0] += 1
 
-**FIXME** why does it happen?
+[Armin: This is a conflict in the transaction module itself; ideally,
+it shouldn't have any, but in order to do that we might need a little bit
+of support from RPython or C code.  So this is pending improvement.]
 
 Tornado modification used in this blog post is based on 3.2.dev2.
 As of now, the latest version is 4.0.2, and if we
@@ -188,6 +190,14 @@
 the same changes to this version, then we no longer get any scaling on this benchmark,
 and there are no conflicts that take any substantial time.
 
+[Armin: There are two possible reactions to a conflict.  We can either
+abort one of the two threads, or (depending on the circumstances) just
+pause the current thread until the other one commits, after which the
+thread will likely be able to continue.  The tool ``print_stm_log.py``
+did not report conflicts that cause pauses.  It has been fixed very
+recently.  Chances are that on this test it would report long pauses and
+point to locations that cause them.]
+
 
 Part 2: a more interesting benchmark: A-star
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