tracemalloc
— 跟踪内存分配
¶
3.4 版新增。
源代码： Lib/tracemalloc.py
The tracemalloc module is a debug tool to trace memory blocks allocated by Python. It provides the following information:
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.
见
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
见
Snapshot.statistics()
for more options.
tracemalloc.
get_object_traceback
(
obj
)
¶
Get the traceback where the Python object
obj
was allocated. Return a
Traceback
instance, or
None
若
tracemalloc
module is not tracing memory allocations or did not trace the allocation of the object.
另请参阅
gc.get_referrers()
and
sys.getsizeof()
函数。
tracemalloc.
get_traceback_limit
(
)
¶
Get the maximum number of frames stored in the traceback of a trace.
tracemalloc
module must be tracing memory allocations to get the limit, otherwise an exception is raised.
The limit is set by the
start()
函数。
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
若
tracemalloc
module is tracing Python memory allocations,
False
否则。
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()
方法。
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
模块。
PYTHONTRACEMALLOC
environment variable (
PYTHONTRACEMALLOC=NFRAME
) and the
-X
tracemalloc=NFRAME
command line option can be used to start tracing at startup.
另请参阅
stop()
,
is_tracing()
and
get_traceback_limit()
函数。
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.
调用
take_snapshot()
function to take a snapshot of traces before clearing them.
另请参阅
start()
,
is_tracing()
and
clear_traces()
函数。
tracemalloc.
take_snapshot
(
)
¶
Take a snapshot of traces of memory blocks allocated by Python. Return a new
Snapshot
实例。
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.
tracemalloc
module must be tracing memory allocations to take a snapshot, see the
start()
函数。
另请参阅
get_object_traceback()
函数。
tracemalloc.
DomainFilter
(
inclusive: bool
,
domain: int
)
¶
Filter traces of memory blocks by their address space (domain).
3.6 版新增。
inclusive
¶
若
inclusive
is
True
(include), match memory blocks allocated in the address space
domain
.
若
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.
tracemalloc.
Filter
(
inclusive: bool
,
filename_pattern: str
,
lineno: int=None
,
all_frames: bool=False
,
domain: int=None
)
¶
Filter on traces of memory blocks.
见
fnmatch.fnmatch()
function for the syntax of
filename_pattern
。
'.pyc'
file extension is replaced with
'.py'
.
范例：
Filter(True,
subprocess.__file__)
only includes traces of the
subprocess
模块
Filter(False,
tracemalloc.__file__)
excludes traces of the
tracemalloc
模块
Filter(False,
"<unknown>")
excludes empty tracebacks
3.5 版改变：
'.pyo'
file extension is no longer replaced with
'.py'
.
3.6 版改变：
添加
domain
属性。
domain
¶
Address space of a memory block (
int
or
None
).
inclusive
¶
若
inclusive
is
True
(include), only match memory blocks allocated in a file with a name matching
filename_pattern
at line number
lineno
.
若
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
¶
若
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
。见
get_traceback_limit()
函数和
Snapshot.traceback_limit
属性。
tracemalloc.
Snapshot
¶
Snapshot of traces of memory blocks allocated by Python.
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
.
见
Snapshot.statistics()
method for
key_type
and
cumulative
参数。
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
.
filter_traces
(
filters
)
¶
创建新的
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.
3.6 版改变：
DomainFilter
instances are now also accepted in
filters
.
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 |
若
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
实例。
The sequence has an undefined order. Use the
Snapshot.statistics()
method to get a sorted list of statistics.
tracemalloc.
Statistic
¶
Statistic on memory allocations.
Snapshot.statistics()
returns a list of
Statistic
实例。
另请参阅
StatisticDiff
类。
count
¶
Number of memory blocks (
int
).
size
¶
Total size of memory blocks in bytes (
int
).
tracemalloc.
StatisticDiff
¶
Statistic difference on memory allocations between an old and a new
Snapshot
实例。
Snapshot.compare_to()
returns a list of
StatisticDiff
instances. See also the
Statistic
类。
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.
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
被使用。
When a snapshot is taken, tracebacks of traces are limited to
get_traceback_limit()
frames. See the
take_snapshot()
函数。
Trace.traceback
attribute is an instance of
Traceback
实例。
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.
类似
traceback.format_tb()
function, except that
format()
does not include newlines.
范例：
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())