[pypy-commit] pypy default: Write down a comment about profopt in JIT-enabled binaries

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: 
Changeset: r87104:4b6221995df7
Date: 2016-09-14 08:49 +0200
http://bitbucket.org/pypy/pypy/changeset/4b6221995df7/

Log:	Write down a comment about profopt in JIT-enabled binaries

diff --git a/pypy/doc/config/translation.profopt.txt b/pypy/doc/config/translation.profopt.txt
--- a/pypy/doc/config/translation.profopt.txt
+++ b/pypy/doc/config/translation.profopt.txt
@@ -3,3 +3,14 @@
 RPython program) to gather profile data. Example for pypy-c: "-c 'from
 richards import main;main(); from test import pystone;
 pystone.main()'"
+
+NOTE: be aware of what this does in JIT-enabled executables.  What it
+does is instrument and later optimize the C code that happens to run in
+the example you specify, ignoring any execution of the JIT-generated
+assembler.  That means that you have to choose the example wisely.  If
+it is something that will just generate assembler and stay there, there
+is little value.  If it is something that exercises heavily library
+routines that are anyway written in C, then it will optimize that.  Most
+interesting would be something that causes a lot of JIT-compilation,
+like running a medium-sized test suite several times in a row, in order
+to optimize the warm-up in general.