Original report at SourceForge, opened Wed Dec 1 19:00:17 2010

The attached minimal strip chart widget shows a serious memory leak, at least on Mac OS X 10.5 and 10.6. I'm using matplotlib 1.0.0 (from the binary installer), Python 2.6 from python.org, numpy 1.5.0 and ActiveState Aqua Tcl/Tk 8.4.19 (the example uses TkAgg).

Michael Droettboom tested the same example using Fedora 14/Python 2.7/Numpy 1.5.1/Tkinter with both matplotlib 1.0 and
matplotlib SVN head and found no leak. Thus it may be specific to Mac OS X or Tcl/Tk 8.4.19.

SourceForge Comments

On Tue Dec 14 19:10:24 2010, reowen wrote:

More information on linux: if I build matplotlib svn trunk rev8840 from source and then run the example it starts out with a slow memory leak (as shown in the last comment) and then grows. However, if I run the example again it starts out leaking at a higher rate and it's not clear if the rate grows with time. For example:

bash-3.2$ python matplotlibMemoryLeak.py
matplotlib.file= /astro/users/rowen/build/matplotlib-trunk/build/lib.linux-x86_64-2.6/matplotlib/init.pyc
time rss memory mem/sec
(sec) (kb) (kb/sec)
0.0 34164 nan
5.0 34440 nan
10.0 34464 4.8
15.1 34492 5.2
20.1 34508 4.5
25.1 34544 5.2
30.2 34556 4.6
35.2 34576 4.5
40.2 34600 4.6
45.2 34616 4.4
50.2 34632 4.2
55.2 34652 4.2
60.3 34664 4.1
65.3 34684 4.0
70.3 34700 4.0
...
346.7 35688 3.7
351.7 35712 3.7
356.7 35724 3.7
361.8 35748 3.7
366.8 35760 3.6
371.8 35784 3.7
376.8 35796 3.6
381.9 35820 3.7
386.9 35832 3.6
391.9 35932 3.9
396.9 35960 3.9
401.9 35976 3.9
407.0 35988 3.9
412.0 36012 3.9
417.0 36024 3.8
422.0 36048 3.9
427.1 36060 3.8
432.1 36084 3.8
437.1 36096 3.8
442.1 36120 3.8
447.1 36132 3.8
452.1 36156 3.8
457.2 36168 3.8
...
572.8 36588 3.8
577.8 36604 3.8
582.8 36624 3.8
587.8 36640 3.8
592.8 36660 3.8
597.9 36672 3.8
602.9 36692 3.8

It appears something is being cached (otherwise why is the leakage in the first run different than all subsequent runs) but it's not in ~/.matplotlib since deleting that makes no difference.

On Tue Dec 14 16:32:56 2010, reowen wrote:

I tried the test script on linux using matplotlib svn trunk rev8840
(which appears to include your patch) and found a leak that starts out
small but gets systematically larger. This is with Python 2.6.5 and
Tkinter built against Tcl/Tk 8.4.13.

time rss memory mem/sec
(sec) (kb) (kb/sec)
0.0 36816 nan
5.0 36860 nan
10.0 36860 0.0
15.1 36860 0.0
20.1 36860 0.0
25.1 36896 1.8
...
326.5 36896 0.1
331.6 36972 0.3
...
401.9 36972 0.3
406.9 36980 0.3
411.9 37004 0.4
417.0 37016 0.4
422.0 37040 0.4
427.0 37052 0.5
432.0 37076 0.5
437.1 37088 0.5
442.1 37112 0.6
447.1 37124 0.6
452.1 37148 0.6
457.2 37160 0.7
462.2 37184 0.7
467.2 37196 0.7
472.2 37220 0.8
477.3 37232 0.8
482.3 37256 0.8
487.3 37268 0.8
492.3 37292 0.9
497.3 37304 0.9
502.3 37328 0.9
507.4 37340 1.0
512.4 37360 1.0
517.4 37376 1.0
522.4 37396 1.0
527.5 37412 1.1
532.5 37432 1.1
537.5 37448 1.1
542.5 37472 1.1
547.6 37488 1.2
552.6 37504 1.2
557.6 37516 1.2
562.6 37540 1.2
567.6 37556 1.2
572.7 37576 1.3
577.7 37592 1.3
582.7 37612 1.3
587.7 37628 1.3
592.7 37648 1.3
597.8 37664 1.4
602.8 37684 1.4
607.8 37700 1.4

This is different behavior than on Mac OS X (where it starts out large and stays about the same), but still alarming.

On Thu Dec 9 17:54:36 2010, reowen wrote:

It is actually the call to canvas.draw that does the leak. Is it not supposed to be called multiple times?

On Thu Dec 9 17:42:17 2010, reowen wrote:

The leak shows up on unix as well. It seems to occur whenever the X axes limits are changed (something that happens frequently for a strip chart). See the new attached script which is much simpler than the first one and reports memory usage. The leak rate is at least roughly proportional to how frequently the x axes are changed (the value of updateInterval).

SourceForge History

• On Fri Dec 10 12:41:15 2010, by reowen: summary: memory leak on Mac with animated plot
• On Thu Dec 9 17:51:44 2010, by reowen: File Added: 395716: matplotlibMemoryLeak.py
• On Thu Dec 9 17:51:20 2010, by reowen: File Deleted: 395715:
• On Thu Dec 9 17:40:25 2010, by reowen: File Added: 395715: matplotlibMemoryLeak.py
• On Wed Dec 1 19:00:18 2010, by reowen: File Added: 394994: MinimalStripChartWdg.py