scipy: memory usage after running scipy.signal.fftconvolve (possible memory leak?)

Consider the memory usage of the following code after executing each statement:

import numpy
import scipy.signal
import gc

# memory at this point is ~35mb

a = numpy.ones(10**7)
b = numpy.ones(10**7)

# memory at this point is ~187mb

c = scipy.signal.fftconvolve(a, numpy.flipud(b), mode="full")

# memory usage at this point is 645mb
# given that a,b,c take up about 305mb in total, this is much
# larger than expected

# If we delete a,b,c and garbage collect...

del a,b,c
gc.collect()

# ...the memory usage drops to ~340mb which is a drop of 305mb
# (as expected since that is the size of what we deleted)
# but the remaining memory usage is still 340mb
# which is much larger than the starting value of 35 mb

Is this extra several hundred mb of memory usage a bug?

Platform:

• CPython 3.5.1 x64
• Scipy 0.17.0 (Christoph Golke’s package)
• Numpy+MKL 1.11.0rc1 (Cristoph Golke’s package)
• Windows 8.1 x64