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Subject: |
which-func-mode slow in long Python tuple |
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Date: |
Fri, 06 Sep 2013 19:47:19 -0500 |
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User-agent: |
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 |
I happen to have a Python source file that has a relatively long tuple
at the module top level, i.e. a Python source file containing:
----------
foo = (
"item 1",
"item 2",
# ...and so on for ~500 lines
)
----------
I also use which-function-mode. If I go to the end of that tuple and
move the cursor in to it, Emacs becomes unusably slow. It will appear
to lock up and eat 100% CPU for 10-20 seconds each time I move the
cursor within the end of that tuple. Emacs remains responsive at the
top of the tuple.
I think this is happening because python-info-current-defun is slow
when dealing with long tuples. (Maybe lists, dicts, and other things
too; I only tested tuples.) Here's some elisp to produce a test case
and benchmark python-info-current-defun:
----------
(progn
(set-buffer (generate-new-buffer "*test*"))
(python-mode)
(insert "foo = (\n")
(dotimes (_ 500) (insert " \"bar\",\n"))
(insert ")\n")
(forward-line -2)
(message "%S" (benchmark-run (python-info-current-defun))))
----------
This makes a python-mode buffer named "*test*" containing only a
500-item Python tuple, as in my above example. On my hardware, the
above benchmark-run yields a result such as "(7.364507 131
0.9572049999999979)", i.e. 7.3 seconds to run.
Once that *test* buffer is created, feel free to turn on
which-function-mode in there and see that Emacs locks up every time you
move the cursor around in the end of that tuple. (which-function-mode
seems to be taking about twice the time reported by benchmark-run.
Perhaps it's calling python-info-current-defun twice?)
I have reproduced this behavior with "emacs -Q" using an Emacs I just
built from trunk, looks like revision 114162. (I get Emacs from Git,
where the master branch is 0f1532f2fe2.) I have also reproduced this
with python.el from the emacs-24 branch, looks like revision 111403.
Thanks to everyone who develops Emacs, an indispensable tool for me!
Dale
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--- Begin Message ---
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Subject: |
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Date: |
Tue, 24 Dec 2013 17:08:09 -0300 |
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User-agent: |
mu4e 0.9.9.6pre2; emacs 24.3.1 |
Fixed in revno 115736.
Thanks Dale for such detailed recipe.
This patch banishes initial thoughts of `python-syntax-context' being a
bad idea. `python-syntax-context' is nothing than a thin semantic
wrapper over `syntax-ppss'. It makes code easier to grasp for newcomers
to Elisp and has almost no impact on itself, it's optional argument is a
`syntax-ppss' list which can be used instead to lower the amount of
calls to it (as it is happening in this new patch I've just committed).
The problem here was that `python-nav-beginning-of-statement' was coded
awfully (looking for the statement beginning line by line). Now it
should be extremely fast compared to that.
Using OP's suggested recipe, here are the elp results for when
which-func is triggered inside the big tuple:
python-info-current-defun 2 0.003719249
0.0018596245
python-nav-beginning-of-defun 2 0.0036946010
0.0018473005
python-nav--beginning-of-defun 2 0.003685751
0.0018428755
python-nav-backward-block 2 0.001836524
0.000918262
python-nav-forward-block 2 0.0018315750
0.0009157875
python-info-looking-at-beginning-of-defun 6 0.000889166
0.0001481943
python-nav-beginning-of-statement 4 0.000437251
0.0001093127
python-syntax-context-type 6 5.009e-06
8.348...e-07
And this is the benchmark-run result: (0.020715153 0 0.0)
Regards,
Fabián.
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