tracemalloc —- 跟踪内存分配

3.4 新版功能.

The tracemalloc module is a debug tool to trace memory blocks allocated byPython. 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 startedas early as possible by setting the PYTHONTRACEMALLOC environmentvariable to 1, or by using -X tracemalloc command lineoption. The tracemalloc.start() function can be called at runtime tostart tracing Python memory allocations.

By default, a trace of an allocated memory block only stores the most recentframe (1 frame). To store 25 frames at startup: set thePYTHONTRACEMALLOC environment variable to 25, or use the-X tracemalloc=25 command line option.

例子

显示前10项

显示内存分配最多的10个文件：

importtracemalloc

tracemalloc.start()

# ... run your application ...

snapshot=tracemalloc.take_snapshot()

top_stats=snapshot.statistics('lineno')

print("[ Top 10 ]")

forstatintop_stats[:10]:

print(stat)

Python测试套件的输出示例：

[Top10]

:716:size=4855KiB,count=39328,average=126B

:284:size=521KiB,count=3199,average=167B

/usr/lib/python3.4/collections/__init__.py:368:size=244KiB,count=2315,average=108B

/usr/lib/python3.4/unittest/case.py:381:size=185KiB,count=779,average=243B

/usr/lib/python3.4/unittest/case.py:402:size=154KiB,count=378,average=416B

/usr/lib/python3.4/abc.py:133:size=88.7KiB,count=347,average=262B

:1446:size=70.4KiB,count=911,average=79B

:1454:size=52.0KiB,count=25,average=2131B

:5:size=49.7KiB,count=148,average=344B

/usr/lib/python3.4/sysconfig.py:411:size=48.0KiB,count=1,average=48.0KiB

We can see that Python loaded 4855 KiB data (bytecode and constants) frommodules and that the collections module allocated 244 KiB to buildnamedtuple types.

计算差异

获取两个快照并显示差异：

importtracemalloc

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 ]")

forstatintop_stats[:10]:

print(stat)

Example of output before/after running some tests of the Python test suite:

[Top10differences]

:716:size=8173KiB(+4428KiB),count=71332(+39369),average=117B

/usr/lib/python3.4/linecache.py:127:size=940KiB(+940KiB),count=8106(+8106),average=119B

/usr/lib/python3.4/unittest/case.py:571:size=298KiB(+298KiB),count=589(+589),average=519B

:284:size=1005KiB(+166KiB),count=7423(+1526),average=139B

/usr/lib/python3.4/mimetypes.py:217:size=112KiB(+112KiB),count=1334(+1334),average=86B

/usr/lib/python3.4/http/server.py:848:size=96.0KiB(+96.0KiB),count=1(+1),average=96.0KiB

/usr/lib/python3.4/inspect.py:1465:size=83.5KiB(+83.5KiB),count=109(+109),average=784B

/usr/lib/python3.4/unittest/mock.py:491:size=77.7KiB(+77.7KiB),count=143(+143),average=557B

/usr/lib/python3.4/urllib/parse.py:476:size=71.8KiB(+71.8KiB),count=969(+969),average=76B

/usr/lib/python3.4/contextlib.py:38:size=67.2KiB(+67.2KiB),count=126(+126),average=546B

We can see that Python has loaded 8173 KiB of module data (bytecode andconstants), and that this is 4428 KiB more than had been loaded before thetests, when the previous snapshot was taken. Similarly, the linecachemodule has cached 940 KiB of Python source code to format tracebacks, allof it since the previous snapshot.

If the system has little free memory, snapshots can be written on disk usingthe Snapshot.dump() method to analyze the snapshot offline. Then use theSnapshot.load() method reload the snapshot.

Get the traceback of a memory block

Code to display the traceback of the biggest memory block:

importtracemalloc

# 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))

forlineinstat.traceback.format():

print(line)

Example of output of the Python test suite (traceback limited to 25 frames):

903memory blocks:870.1KiB

File"",line716

File"",line1036

File"",line934

File"",line1068

File"",line619

File"",line1581

File"",line1614

File"/usr/lib/python3.4/doctest.py",line101

importpdb

File"",line284

File"",line938

File"",line1068

File"",line619

File"",line1581

File"",line1614

File"/usr/lib/python3.4/test/support/__init__.py",line1728

importdoctest

File"/usr/lib/python3.4/test/test_pickletools.py",line21

support.run_doctest(pickletools)

File"/usr/lib/python3.4/test/regrtest.py",line1276

test_runner()

File"/usr/lib/python3.4/test/regrtest.py",line976

display_failure=notverbose)

File"/usr/lib/python3.4/test/regrtest.py",line761

match_tests=ns.match_tests)

File"/usr/lib/python3.4/test/regrtest.py",line1563

main()

File"/usr/lib/python3.4/test/__main__.py",line3

regrtest.main_in_temp_cwd()

File"/usr/lib/python3.4/runpy.py",line73

exec(code,run_globals)

File"/usr/lib/python3.4/runpy.py",line160

"__main__",fname,loader,pkg_name)

We can see that the most memory was allocated in the importlib module toload data (bytecode and constants) from modules: 870.1 KiB. The traceback iswhere the importlib loaded data most recently: on the import pdbline of the doctest module. The traceback may change if a new module isloaded.

Pretty top

Code to display the 10 lines allocating the most memory with a pretty output,ignoring and files:

importlinecache

importos

importtracemalloc

defdisplay_top(snapshot,key_type='lineno',limit=10):

snapshot=snapshot.filter_traces((

tracemalloc.Filter(False,""),

tracemalloc.Filter(False,""),

))

top_stats=snapshot.statistics(key_type)

print("Top %s lines"%limit)

forindex,statinenumerate(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()

ifline:

print(' %s'%line)

other=top_stats[limit:]

ifother:

size=sum(stat.sizeforstatinother)

print("%s other: %.1f KiB"%(len(other),size/1024))

total=sum(stat.sizeforstatintop_stats)

print("Total allocated size: %.1f KiB"%(total/1024))

tracemalloc.start()

# ... run your application ...

snapshot=tracemalloc.take_snapshot()

display_top(snapshot)

Python测试套件的输出示例：

Top10lines

#1: Lib/base64.py:414: 419.8 KiB

_b85chars2=[(a+b)forain_b85charsforbin_b85chars]

#2: Lib/base64.py:306: 419.8 KiB

_a85chars2=[(a+b)forain_a85charsforbin_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

forain_hexdigforbin_hexdig}

#8: :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+bforain_b32tabforbin_b32tab]

6220other:3602.8KiB

Totalallocated size:5303.1KiB

API

函数tracemalloc.clear_traces()

Clear traces of memory blocks allocated by Python.

See also stop().

tracemalloc.getobject_traceback(_obj)

Get the traceback where the Python object obj was allocated.Return a Traceback instance, or None if the tracemallocmodule is not tracing memory allocations or did not trace the allocation ofthe object.

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 toget 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 thetracemalloc module as a tuple: (current: int, peak: int).

tracemalloc.get_tracemalloc_memory()

Get the memory usage in bytes of the tracemalloc module used to storetraces of memory blocks.Return an int.

tracemalloc.is_tracing()

True if the tracemalloc module is tracing Python memoryallocations, False otherwise.

See also start() and stop() functions.

tracemalloc.start(nframe: int=1)

Start tracing Python memory allocations: install hooks on Python memoryallocators. Collected tracebacks of traces will be limited to nframe_frames. By default, a trace of a memory block only stores the most recentframe: the limit is 1. _nframe must be greater or equal to 1.

Storing more than 1 frame is only useful to compute statistics groupedby 'traceback' or to compute cumulative statistics: see theSnapshot.compare_to() and Snapshot.statistics() methods.

Storing more frames increases the memory and CPU overhead of thetracemalloc module. Use the get_tracemalloc_memory() functionto measure how much memory is used by the tracemalloc module.

The PYTHONTRACEMALLOC environment variable(PYTHONTRACEMALLOC=NFRAME) and the -X tracemalloc=NFRAMEcommand line option can be used to start tracing at startup.

tracemalloc.stop()

Stop tracing Python memory allocations: uninstall hooks on Python memoryallocators. Also clears all previously collected traces of memory blocksallocated by Python.

Call take_snapshot() function to take a snapshot of traces beforeclearing them.

tracemalloc.take_snapshot()

Take a snapshot of traces of memory blocks allocated by Python. Return a newSnapshot instance.

The snapshot does not include memory blocks allocated before thetracemalloc module started to trace memory allocations.

Tracebacks of traces are limited to get_traceback_limit() frames. Usethe nframe parameter of the start() function to store more frames.

The tracemalloc module must be tracing memory allocations to take asnapshot, see the start() function.

域过滤器classtracemalloc.DomainFilter(inclusive: bool, domain: int)

Filter traces of memory blocks by their address space (domain).

3.6 新版功能.

inclusive

If inclusive is True (include), match memory blocks allocatedin the address space domain.

If inclusive is False (exclude), match memory blocks not allocatedin the address space domain.

domain

Address space of a memory block (int). Read-only property.

过滤器classtracemalloc.Filter(inclusive: bool, filename_pattern: str, lineno: int=None, all_frames: bool=False, domain: int=None)

对内存块的跟踪进行筛选。

See the fnmatch.fnmatch() function for the syntax offilename_pattern. The '.pyc' file extension isreplaced with '.py'.

示例：

Filter(True, subprocess.file) only includes traces of thesubprocess module

Filter(False, tracemalloc.file) excludes traces of thetracemalloc module

Filter(False, "") excludes empty tracebacks

在 3.5 版更改: The '.pyo' file extension is no longer replaced with '.py'.

在 3.6 版更改: Added the domain attribute.

domain

Address space of a memory block (int or None).

tracemalloc uses the domain 0 to trace memory allocations made byPython. C extensions can use other domains to trace other resources.

inclusive

If inclusive is True (include), only match memory blocks allocatedin a file with a name matching filename_pattern at line numberlineno.

If inclusive is False (exclude), ignore memory blocks allocated ina file with a name matching filename_pattern at line numberlineno.

lineno

Line number (int) of the filter. If lineno is None, the filtermatches 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. Ifall_frames is False, only the most recent frame is checked.

This attribute has no effect if the traceback limit is 1. See theget_traceback_limit() function and Snapshot.traceback_limitattribute.

Frameclasstracemalloc.Frame

Frame of a traceback.

The Traceback class is a sequence of Frame instances.

filename

文件名(str).

lineno

行号 (int).

快照classtracemalloc.Snapshot

Snapshot of traces of memory blocks allocated by Python.

The take_snapshot() function creates a snapshot instance.

compareto(_old_snapshot: Snapshot, key_type: str, cumulative: bool=False)

Compute the differences with an old snapshot. Get statistics as a sortedlist 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 valueof StatisticDiff.size_diff, StatisticDiff.size, absolutevalue of StatisticDiff.count_diff, Statistic.count andthen by StatisticDiff.traceback.

dump(filename)

将快照写入文件

使用 load() 重载快照。

filtertraces(_filters)

Create a new Snapshot instance with a filtered tracessequence, filters is a list of DomainFilter andFilter instances. If filters is an empty list, return a newSnapshot instance with a copy of the traces.

All inclusive filters are applied at once, a trace is ignored if noinclusive filters match it. A trace is ignored if at least one exclusivefilter matches it.

在 3.6 版更改: DomainFilter instances are now also accepted in filters.

classmethodload(filename)

从文件载入快照。

statistics(key_type: str, cumulative: bool=False)

获取 Statistic 信息列表，按 key_type 分组排序：

key_type

描述

'filename'

filename

'lineno'

文件名和行号

'traceback'

回溯

If cumulative is True, cumulate size and count of memory blocks ofall 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 byStatistic.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 ofTrace instances.

The sequence has an undefined order. Use the Snapshot.statistics()method to get a sorted list of statistics.

统计classtracemalloc.Statistic

统计内存分配

count

内存块数(整形)。

size

Total size of memory blocks in bytes (int).

traceback

Traceback where the memory block was allocated, Tracebackinstance.

StatisticDiffclasstracemalloc.StatisticDiff

Statistic difference on memory allocations between an old and a newSnapshot instance.

Snapshot.compare_to() returns a list of StatisticDiffinstances. See also the Statistic class.

count

Number of memory blocks in the new snapshot (int): 0 ifthe memory blocks have been released in the new snapshot.

count_diff

Difference of number of memory blocks between the old and the newsnapshots (int): 0 if the memory blocks have been allocated inthe 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 andthe new snapshots (int): 0 if the memory blocks have beenallocated in the new snapshot.

traceback

Traceback where the memory blocks were allocated, Tracebackinstance.

跟踪classtracemalloc.Trace

Trace of a memory block.

The Snapshot.traces attribute is a sequence of Traceinstances.

在 3.6 版更改: Added the domain attribute.

domain

Address space of a memory block (int). Read-only property.

tracemalloc uses the domain 0 to trace memory allocations made byPython. C extensions can use other domains to trace other resources.

size

Size of the memory block in bytes (int).

traceback

Traceback where the memory block was allocated, Tracebackinstance.

回溯classtracemalloc.Traceback

Sequence of Frame instances sorted from the oldest frame to themost recent frame.

A traceback contains at least 1 frame. If the tracemalloc modulefailed to get a frame, the filename "" at line number 0 isused.

When a snapshot is taken, tracebacks of traces are limited toget_traceback_limit() frames. See the take_snapshot() function.

The Trace.traceback attribute is an instance of Tracebackinstance.

在 3.7 版更改: Frames are now sorted from the oldest to the most recent, instead of most recent to oldest.

format(limit=None, most_recent_first=False)

Format the traceback as a list of lines with newlines. Use thelinecache module to retrieve lines from the source code.If limit is set, format the limit most recent frames if limit_is positive. Otherwise, format the abs(limit) oldest frames.If _most_recent_first is True, the order of the formatted framesis reversed, returning the most recent frame first instead of last.

Similar to the traceback.format_tb() function, except thatformat() does not include newlines.

示例:

print("Traceback (most recent call first):")

forlineintraceback:

print(line)

输出:

Traceback(most recent call first):

File"test.py",line9

obj=Object()

File"test.py",line12

tb=tracemalloc.get_object_traceback(f())