I can add a couple of things to item (1) below. First, the problem
occurs only with toolbar2, not with classic or None. Second, a script
that illustrates it is attached.
Eric
Eric Firing wrote:
In 2007, two different major memory leaks have been identified:
1) Eric Pellegrini showed that a loop over figure(); close() leaks. I
have verified that this occurs with any interactive backend, but not
with non-interactive backends. This may be the same problem that was
reported in other messages, such as one by Dylan Passmore in January.
2) There is a recent thread "Re: Memory leak in basemap or matplotlib"
showing that even with a non-interactive backend, a seemingly-pointless
call to cla() is needed to prevent a leak.
I would like to suggest that we try harder to solve these problems ASAP.
This kind of malfunctioning at the core of mpl worries me.
I have spent quite a bit of time trying to figure out (1), and I have
tracked it down to the NavigationToolbar2. Eliminate the toolbar by
putting None in the rc slot, and the memory leak vanishes. It looks to
me like some explicit call to a destroy method may be needed to
dismantle the toolbar when a figure is closed and/or deleted. I suspect
that each gui toolkit is keeping references to components, and the
toolbar is not getting the word when the window is destroyed.
gc.garbage verifies that the toolbar components are what get left behind.
So, I hope a gui toolkit backend wizard can step forward and say, "Of
course, we just need to put a __del__ method here with a call to
destroy()", or something like that.
I have spent much less time on (2), and made no progress.
We are relying very heavily on the gc--mpl has cyclic references all
over the place. Is anyone sure that we don't need explicit gc support
in any of the extension code? Can *everything* in the extension code be
handled correctly with reference counting? Is this independent of how
things defined in extension code are used at the python level?
It is not clear to me that gc debugging methods even allow one to see
problems in extension code that do not have some degree of gc support.
The standard documentation of the gc module and the gc C API is minimal.
Eric
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#!/usr/bin/env python
'''
This illustrates a leak that occurs with any interactive backend.
'''
import os, sys, time
import gc
import matplotlib
matplotlib.use('TkAgg') # or TkAgg or WxAgg or QtAgg or Gtk
matplotlib.rcParams['toolbar'] = 'toolbar2' # None, classic, toolbar2
import pylab
from matplotlib import _pylab_helpers as ph
def report_memory(i):
pid = os.getpid()
a2 = os.popen('ps -p %d -o rss,sz' % pid).readlines()
print i, ' ', a2[1],
return int(a2[1].split()[1])
gc.disable()
#gc.set_debug(gc.DEBUG_LEAK)
gc.set_debug(gc.DEBUG_UNCOLLECTABLE
| gc.DEBUG_INSTANCES | gc.DEBUG_OBJECTS)
# take a memory snapshot on indStart and compare it with indEnd
indStart, indEnd = 30, 50
for i in range(indEnd):
fig = pylab.figure()
print 'after figure, unreachable:', gc.collect()
print 'total uncollectable:', len(gc.garbage)
#report_memory(i)
#fig.clear()
#pylab.cla() #no effect
#pylab.clf() # no effect
#pylab.show() # makes it worse
pylab.close()
#del(fig)
#gc.collect() #no effect
val = report_memory(i)
print 'after close, unreachable:', gc.collect()
print 'total uncollectable:', len(gc.garbage)
del(fig)
print 'after del(fig), unreachable:', gc.collect()
print 'total uncollectable:',len(gc.garbage)
if i==indStart: start = val # wait a few cycles for memory usage to stabilize
gc.collect()
print
print 'uncollectable list:', gc.garbage
print
end = val
if i > indStart:
print 'Average memory consumed per loop: %1.4fk bytes\n' % ((end-start)/float(indEnd-indStart))
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