Author: Antonio Cuni <anto.c...@gmail.com> Branch: extradoc Changeset: r3880:0079f4a8086c Date: 2011-08-12 11:49 +0200 http://bitbucket.org/pypy/extradoc/changeset/0079f4a8086c/
Log: review and expand the blog post diff --git a/blog/draft/jitviewer.rst b/blog/draft/jitviewer.rst --- a/blog/draft/jitviewer.rst +++ b/blog/draft/jitviewer.rst @@ -4,25 +4,55 @@ Hello. We're proud to announce the first public release of the jitviewer. As of now, -jitviewer is a slightly internal tool that helps understanding how PyPy's JIT -compiles Python down all the way to assembler. If you want to give it a go, -clone the `repository`_ and look up the README. You also need both the PyPy -`source code checkout`_ and a fairly recent compiled PyPy executable, like -`a nightly`_ one. If you want to look first what does it do, check out -`the online demo`_. +jitviewer is a slightly internal tool that helps understanding how your Python +source code is compiled by the PyPy's JIT all the way down to machine code. -.. _`repository`: http://bitbucket.org/pypy/jitviewer +To install it, you need a recent version of PyPy, for example one of the +`nightly builds`_: + + - install ``pip`` and ``distribute`` either by creating a PyPy virtualenv_ + or by following the `installation instructions`_. + + - make sure to have a `source code checkout`_ of PyPy and put it in your + PYTHONPATH. + + - ``pip install jitviewer``. Note that you need to run the ``pip`` + executable which belongs to PyPy, not the globally installed one. + +Have a look at the README_ for how to start it, or try the `online demo`_ if +you just want to play with it. + +The jitviewer is a web application written with ``flask`` and ``jinja2``. If +you have experience with web development and you want to help PyPy, don't +hesitate to contact us, there are plenty of things to improve in it :-). + .. _`source code checkout`: http://bitbucket.org/pypy/pypy -.. _`a nightly`: http://buildbot.pypy.org/nightly/trunk/ -.. _`the online demo`: http://wyvern.cs.uni-duesseldorf.de:5000/ +.. _`nightly builds`: http://buildbot.pypy.org/nightly/trunk/ +.. _`online demo`: http://wyvern.cs.uni-duesseldorf.de:5000/ +.. _virtualenv: http://pypi.python.org/pypi/virtualenv +.. _`installation instructions`: http://doc.pypy.org/en/latest/getting-started.html#installing-pypy +.. _README: http://bitbucket.org/pypy/jitviewer/src/24adc3403cd8/README + What does the jitviewer really do? ---------------------------------- -In short - it displays how exactly the JIT has compiled python source code -into assembler in a hierarchical way. It displays four levels: +At the top of the page, you will see the list of pieces of code which has been +compiled by the JIT. You will see entries for both normal loops and for +"entry bridges". This is not the right place to discuss the difference +between those, but you most probably want to look at loops, because usually +it's where most of the time is spent. -* Python source code +Note that for each loop, you will see the name of the function which contains +the **first** instruction of the loop. However, thanks to the inlining done +by the JIT, it will contain also the code for other functions. + +Once you select a loop, the jitviewer shows how the JIT has compiled the +Python source code into assembler in a hierarchical way. It displays four +levels: + +* Python source code: only the lines shown in azure have been compiled for + this particular loop, the ones in gray have not. * Python bytecode, the one you would get by doing:: @@ -32,15 +62,18 @@ import dis dis.dis(f) - This looks like LOAD\_FAST, LOAD\_GLOBAL etc. + The opcodes are e.g. ``LOAD\_FAST``, ``LOAD\_GLOBAL`` etc. The opcodes + which are not in bold have been completely optimized aways by the JIT. * Intermediate representation of jit code (IR). This is a combination of operations (like integer addition, reading fields out of structures) and - guards (aborting assembler if invariants are invalidated). Guards are in red. - Those operations operate on machine-level objects, like integers and memory - locations. + guards (which check that the assumptions we made are actually true). Guards + are in red. These operations are "at the same level as C": so, for example, + ``int_add`` takes two unboxed integers which can be stored into the register + of the CPU. -* Assembler +* Assembler: you can see it by clicking on "Show assembler" in the menu on the + right. Sometimes you'll find that a guard fails often enough that a new piece of assembler is required to be compiled. This is an alternative path through the @@ -50,6 +83,7 @@ .. _`jit documentation`: http://doc.pypy.org/en/latest/jit/index.html + I'm still confused ------------------ @@ -60,4 +94,4 @@ .. _`contact`: http://pypy.org/contact.html Cheers, -fijal +fijal & antocuni _______________________________________________ pypy-commit mailing list pypy-commit@python.org http://mail.python.org/mailman/listinfo/pypy-commit
