tracemalloc --- Trace memory allocationsNew in version 3.4.
Source code: Lib/tracemalloc.py
[UNKNOWN NODE transition]The tracemalloc module is a debug tool to trace memory blocks allocated by Python. It provides the following information:
- Traceback where an object was allocated
- Statistics on allocated memory blocks per filename and per line number: total size, number and average size of allocated memory blocks
- Compute the differences between two snapshots to detect memory leaks
To trace most memory blocks allocated by Python, the module should be started
as early as possible by setting the PYTHONTRACEMALLOC environment
variable to 1, or by using -X tracemalloc command line
option. The tracemalloc.start() function can be called at runtime to
start tracing Python memory allocations.
By default, a trace of an allocated memory block only stores the most recent
frame (1 frame). To store 25 frames at startup: set the
PYTHONTRACEMALLOC environment variable to 25, or use the
-X tracemalloc=25 command line option.
Display the 10 files allocating the most memory:
import tracemalloc
tracemalloc.start()
# ... run your application ...
snapshot = tracemalloc.take_snapshot()
top_stats = snapshot.statistics('lineno')
print("[ Top 10 ]")
for stat in top_stats[:10]:
print(stat)
Example of output of the Python test suite:
[ Top 10 ]
<frozen importlib._bootstrap>:716: size=4855 KiB, count=39328, average=126 B
<frozen importlib._bootstrap>:284: size=521 KiB, count=3199, average=167 B
/usr/lib/python3.4/collections/__init__.py:368: size=244 KiB, count=2315, average=108 B
/usr/lib/python3.4/unittest/case.py:381: size=185 KiB, count=779, average=243 B
/usr/lib/python3.4/unittest/case.py:402: size=154 KiB, count=378, average=416 B
/usr/lib/python3.4/abc.py:133: size=88.7 KiB, count=347, average=262 B
<frozen importlib._bootstrap>:1446: size=70.4 KiB, count=911, average=79 B
<frozen importlib._bootstrap>:1454: size=52.0 KiB, count=25, average=2131 B
<string>:5: size=49.7 KiB, count=148, average=344 B
/usr/lib/python3.4/sysconfig.py:411: size=48.0 KiB, count=1, average=48.0 KiB
We can see that Python loaded 4855 KiB data (bytecode and constants) from
modules and that the collections module allocated 244 KiB to build
namedtuple types.
See Snapshot.statistics() for more options.
Take two snapshots and display the differences:
import tracemalloc
tracemalloc.start()
# ... start your application ...
snapshot1 = tracemalloc.take_snapshot()
# ... call the function leaking memory ...
snapshot2 = tracemalloc.take_snapshot()
top_stats = snapshot2.compare_to(snapshot1, 'lineno')
print("[ Top 10 differences ]")
for stat in top_stats[:10]:
print(stat)
Example of output before/after running some tests of the Python test suite:
[ Top 10 differences ]
<frozen importlib._bootstrap>:716: size=8173 KiB (+4428 KiB), count=71332 (+39369), average=117 B
/usr/lib/python3.4/linecache.py:127: size=940 KiB (+940 KiB), count=8106 (+8106), average=119 B
/usr/lib/python3.4/unittest/case.py:571: size=298 KiB (+298 KiB), count=589 (+589), average=519 B
<frozen importlib._bootstrap>:284: size=1005 KiB (+166 KiB), count=7423 (+1526), average=139 B
/usr/lib/python3.4/mimetypes.py:217: size=112 KiB (+112 KiB), count=1334 (+1334), average=86 B
/usr/lib/python3.4/http/server.py:848: size=96.0 KiB (+96.0 KiB), count=1 (+1), average=96.0 KiB
/usr/lib/python3.4/inspect.py:1465: size=83.5 KiB (+83.5 KiB), count=109 (+109), average=784 B
/usr/lib/python3.4/unittest/mock.py:491: size=77.7 KiB (+77.7 KiB), count=143 (+143), average=557 B
/usr/lib/python3.4/urllib/parse.py:476: size=71.8 KiB (+71.8 KiB), count=969 (+969), average=76 B
/usr/lib/python3.4/contextlib.py:38: size=67.2 KiB (+67.2 KiB), count=126 (+126), average=546 B
We can see that Python has loaded 8173 KiB of module data (bytecode and
constants), and that this is 4428 KiB more than had been loaded before the
tests, when the previous snapshot was taken. Similarly, the linecache
module has cached 940 KiB of Python source code to format tracebacks, all
of it since the previous snapshot.
If the system has little free memory, snapshots can be written on disk using
the Snapshot.dump() method to analyze the snapshot offline. Then use the
Snapshot.load() method reload the snapshot.
Code to display the traceback of the biggest memory block:
import tracemalloc
# Store 25 frames
tracemalloc.start(25)
# ... run your application ...
snapshot = tracemalloc.take_snapshot()
top_stats = snapshot.statistics('traceback')
# pick the biggest memory block
stat = top_stats[0]
print("%s memory blocks: %.1f KiB" % (stat.count, stat.size / 1024))
for line in stat.traceback.format():
print(line)
Example of output of the Python test suite (traceback limited to 25 frames):
903 memory blocks: 870.1 KiB
File "<frozen importlib._bootstrap>", line 716
File "<frozen importlib._bootstrap>", line 1036
File "<frozen importlib._bootstrap>", line 934
File "<frozen importlib._bootstrap>", line 1068
File "<frozen importlib._bootstrap>", line 619
File "<frozen importlib._bootstrap>", line 1581
File "<frozen importlib._bootstrap>", line 1614
File "/usr/lib/python3.4/doctest.py", line 101
import pdb
File "<frozen importlib._bootstrap>", line 284
File "<frozen importlib._bootstrap>", line 938
File "<frozen importlib._bootstrap>", line 1068
File "<frozen importlib._bootstrap>", line 619
File "<frozen importlib._bootstrap>", line 1581
File "<frozen importlib._bootstrap>", line 1614
File "/usr/lib/python3.4/test/support/__init__.py", line 1728
import doctest
File "/usr/lib/python3.4/test/test_pickletools.py", line 21
support.run_doctest(pickletools)
File "/usr/lib/python3.4/test/regrtest.py", line 1276
test_runner()
File "/usr/lib/python3.4/test/regrtest.py", line 976
display_failure=not verbose)
File "/usr/lib/python3.4/test/regrtest.py", line 761
match_tests=ns.match_tests)
File "/usr/lib/python3.4/test/regrtest.py", line 1563
main()
File "/usr/lib/python3.4/test/__main__.py", line 3
regrtest.main_in_temp_cwd()
File "/usr/lib/python3.4/runpy.py", line 73
exec(code, run_globals)
File "/usr/lib/python3.4/runpy.py", line 160
"__main__", fname, loader, pkg_name)
We can see that the most memory was allocated in the importlib module to
load data (bytecode and constants) from modules: 870.1 KiB. The traceback is
where the importlib loaded data most recently: on the import pdb
line of the doctest module. The traceback may change if a new module is
loaded.
Code to display the 10 lines allocating the most memory with a pretty output,
ignoring <frozen importlib._bootstrap> and <unknown> files:
import linecache
import os
import tracemalloc
def display_top(snapshot, key_type='lineno', limit=10):
snapshot = snapshot.filter_traces((
tracemalloc.Filter(False, "<frozen importlib._bootstrap>"),
tracemalloc.Filter(False, "<unknown>"),
))
top_stats = snapshot.statistics(key_type)
print("Top %s lines" % limit)
for index, stat in enumerate(top_stats[:limit], 1):
frame = stat.traceback[0]
# replace "/path/to/module/file.py" with "module/file.py"
filename = os.sep.join(frame.filename.split(os.sep)[-2:])
print("#%s: %s:%s: %.1f KiB"
% (index, filename, frame.lineno, stat.size / 1024))
line = linecache.getline(frame.filename, frame.lineno).strip()
if line:
print(' %s' % line)
other = top_stats[limit:]
if other:
size = sum(stat.size for stat in other)
print("%s other: %.1f KiB" % (len(other), size / 1024))
total = sum(stat.size for stat in top_stats)
print("Total allocated size: %.1f KiB" % (total / 1024))
tracemalloc.start()
# ... run your application ...
snapshot = tracemalloc.take_snapshot()
display_top(snapshot)
Example of output of the Python test suite:
Top 10 lines
#1: Lib/base64.py:414: 419.8 KiB
_b85chars2 = [(a + b) for a in _b85chars for b in _b85chars]
#2: Lib/base64.py:306: 419.8 KiB
_a85chars2 = [(a + b) for a in _a85chars for b in _a85chars]
#3: collections/__init__.py:368: 293.6 KiB
exec(class_definition, namespace)
#4: Lib/abc.py:133: 115.2 KiB
cls = super().__new__(mcls, name, bases, namespace)
#5: unittest/case.py:574: 103.1 KiB
testMethod()
#6: Lib/linecache.py:127: 95.4 KiB
lines = fp.readlines()
#7: urllib/parse.py:476: 71.8 KiB
for a in _hexdig for b in _hexdig}
#8: <string>:5: 62.0 KiB
#9: Lib/_weakrefset.py:37: 60.0 KiB
self.data = set()
#10: Lib/base64.py:142: 59.8 KiB
_b32tab2 = [a + b for a in _b32tab for b in _b32tab]
6220 other: 3602.8 KiB
Total allocated size: 5303.1 KiB
See Snapshot.statistics() for more options.
tracemalloc.clear_traces()
Clear traces of memory blocks allocated by Python.
See also stop().
tracemalloc.get_object_traceback(obj)
Get the traceback where the Python object obj was allocated.
Return a Traceback instance, or None if the tracemalloc
module is not tracing memory allocations or did not trace the allocation of
the object.
See also gc.get_referrers() and sys.getsizeof() functions.
tracemalloc.get_traceback_limit()
Get the maximum number of frames stored in the traceback of a trace.
The tracemalloc module must be tracing memory allocations to
get the limit, otherwise an exception is raised.
The limit is set by the start() function.
tracemalloc.get_traced_memory()
Get the current size and peak size of memory blocks traced by the
tracemalloc module as a tuple: (current: int, peak: int).
tracemalloc.get_tracemalloc_memory()
Get the memory usage in bytes of the tracemalloc module used to store
traces of memory blocks.
Return an int.
tracemalloc.is_tracing()
True if the tracemalloc module is tracing Python memory
allocations, False otherwise.
tracemalloc.start(nframe: int=1)
Start tracing Python memory allocations: install hooks on Python memory
allocators. Collected tracebacks of traces will be limited to nframe
frames. By default, a trace of a memory block only stores the most recent
frame: the limit is 1. nframe must be greater or equal to 1.
Storing more than 1 frame is only useful to compute statistics grouped
by 'traceback' or to compute cumulative statistics: see the
Snapshot.compare_to() and Snapshot.statistics() methods.
Storing more frames increases the memory and CPU overhead of the
tracemalloc module. Use the get_tracemalloc_memory() function
to measure how much memory is used by the tracemalloc module.
The PYTHONTRACEMALLOC environment variable
(PYTHONTRACEMALLOC=NFRAME) and the -X tracemalloc=NFRAME
command line option can be used to start tracing at startup.
See also stop(), is_tracing() and get_traceback_limit()
functions.
tracemalloc.stop()
Stop tracing Python memory allocations: uninstall hooks on Python memory allocators. Also clears all previously collected traces of memory blocks allocated by Python.
Call take_snapshot() function to take a snapshot of traces before
clearing them.
See also start(), is_tracing() and clear_traces()
functions.
tracemalloc.take_snapshot()
Take a snapshot of traces of memory blocks allocated by Python. Return a new
Snapshot instance.
The snapshot does not include memory blocks allocated before the
tracemalloc module started to trace memory allocations.
Tracebacks of traces are limited to get_traceback_limit() frames. Use
the nframe parameter of the start() function to store more frames.
The tracemalloc module must be tracing memory allocations to take a
snapshot, see the start() function.
See also the get_object_traceback() function.
class tracemalloc.DomainFilter(inclusive: bool, domain: int)
Filter traces of memory blocks by their address space (domain).
New in version 3.6.
inclusive
If inclusive is True (include), match memory blocks allocated
in the address space domain.
If inclusive is False (exclude), match memory blocks not allocated
in the address space domain.
domain
Address space of a memory block (int). Read-only property.
class tracemalloc.Filter(inclusive: bool, filename_pattern: str, lineno: int=None, all_frames: bool=False, domain: int=None)
Filter on traces of memory blocks.
See the fnmatch.fnmatch() function for the syntax of
filename_pattern. The '.pyc' file extension is
replaced with '.py'.
Examples:
Filter(True, subprocess.__file__)only includes traces of thesubprocessmoduleFilter(False, tracemalloc.__file__)excludes traces of thetracemallocmoduleFilter(False, "<unknown>")excludes empty tracebacks
Changed in version 3.5: The '.pyo' file extension is no longer replaced with '.py'.
Changed in version 3.6: Added the domain attribute.
domain
Address space of a memory block (int or None).
inclusive
If inclusive is True (include), only match memory blocks allocated
in a file with a name matching filename_pattern at line number
lineno.
If inclusive is False (exclude), ignore memory blocks allocated in
a file with a name matching filename_pattern at line number
lineno.
lineno
Line number (int) of the filter. If lineno is None, the filter
matches any line number.
filename_pattern
Filename pattern of the filter (str). Read-only property.
all_frames
If all_frames is True, all frames of the traceback are checked. If
all_frames is False, only the most recent frame is checked.
This attribute has no effect if the traceback limit is 1. See the
get_traceback_limit() function and Snapshot.traceback_limit
attribute.
class tracemalloc.Frame
Frame of a traceback.
The Traceback class is a sequence of Frame instances.
filename
Filename (str).
lineno
Line number (int).
class tracemalloc.Snapshot
Snapshot of traces of memory blocks allocated by Python.
The take_snapshot() function creates a snapshot instance.
compare_to(old_snapshot: Snapshot, key_type: str, cumulative: bool=False)
Compute the differences with an old snapshot. Get statistics as a sorted
list of StatisticDiff instances grouped by key_type.
See the Snapshot.statistics() method for key_type and cumulative
parameters.
The result is sorted from the biggest to the smallest by: absolute value
of StatisticDiff.size_diff, StatisticDiff.size, absolute
value of StatisticDiff.count_diff, Statistic.count and
then by StatisticDiff.traceback.
dump(filename)
Write the snapshot into a file.
Use load() to reload the snapshot.
filter_traces(filters)
Create a new Snapshot instance with a filtered traces
sequence, filters is a list of DomainFilter and
Filter instances. If filters is an empty list, return a new
Snapshot instance with a copy of the traces.
All inclusive filters are applied at once, a trace is ignored if no inclusive filters match it. A trace is ignored if at least one exclusive filter matches it.
Changed in version 3.6: DomainFilter instances are now also accepted in filters.
classmethod load(filename)
Load a snapshot from a file.
See also dump().
statistics(key_type: str, cumulative: bool=False)
Get statistics as a sorted list of Statistic instances grouped
by key_type:
| key_type | description |
|---|---|
'filename' | filename |
'lineno' | filename and line number |
'traceback' | traceback |
If cumulative is True, cumulate size and count of memory blocks of
all frames of the traceback of a trace, not only the most recent frame.
The cumulative mode can only be used with key_type equals to
'filename' and 'lineno'.
The result is sorted from the biggest to the smallest by:
Statistic.size, Statistic.count and then by
Statistic.traceback.
traceback_limit
Maximum number of frames stored in the traceback of traces:
result of the get_traceback_limit() when the snapshot was taken.
traces
Traces of all memory blocks allocated by Python: sequence of
Trace instances.
The sequence has an undefined order. Use the Snapshot.statistics()
method to get a sorted list of statistics.
class tracemalloc.Statistic
Statistic on memory allocations.
Snapshot.statistics() returns a list of Statistic instances.
See also the StatisticDiff class.
count
Number of memory blocks (int).
size
Total size of memory blocks in bytes (int).
traceback
Traceback where the memory block was allocated, Traceback
instance.
class tracemalloc.StatisticDiff
Statistic difference on memory allocations between an old and a new
Snapshot instance.
Snapshot.compare_to() returns a list of StatisticDiff
instances. See also the Statistic class.
count
Number of memory blocks in the new snapshot (int): 0 if
the memory blocks have been released in the new snapshot.
count_diff
Difference of number of memory blocks between the old and the new
snapshots (int): 0 if the memory blocks have been allocated in
the new snapshot.
size
Total size of memory blocks in bytes in the new snapshot (int):
0 if the memory blocks have been released in the new snapshot.
size_diff
Difference of total size of memory blocks in bytes between the old and
the new snapshots (int): 0 if the memory blocks have been
allocated in the new snapshot.
traceback
Traceback where the memory blocks were allocated, Traceback
instance.
class tracemalloc.Trace
Trace of a memory block.
The Snapshot.traces attribute is a sequence of Trace
instances.
size
Size of the memory block in bytes (int).
traceback
Traceback where the memory block was allocated, Traceback
instance.
class tracemalloc.Traceback
Sequence of Frame instances sorted from the most recent frame to
the oldest frame.
A traceback contains at least 1 frame. If the tracemalloc module
failed to get a frame, the filename "<unknown>" at line number 0 is
used.
When a snapshot is taken, tracebacks of traces are limited to
get_traceback_limit() frames. See the take_snapshot() function.
The Trace.traceback attribute is an instance of Traceback
instance.
format(limit=None)
Format the traceback as a list of lines with newlines. Use the
linecache module to retrieve lines from the source code. If
limit is set, only format the limit most recent frames.
Similar to the traceback.format_tb() function, except that
format() does not include newlines.
Example:
print("Traceback (most recent call first):")
for line in traceback:
print(line)
Output:
Traceback (most recent call first):
File "test.py", line 9
obj = Object()
File "test.py", line 12
tb = tracemalloc.get_object_traceback(f())