Skip to content

Slow inspect.getmodule #92041

Open
Open
@mdeck

Description

@mdeck

Bug report

inspect.getmodule is slow. It becomes slower as len(sys.modules) grows. It is slower with modules that don't resolve to valid file paths. This causes inspect.stack and others to be slow as well.

def run_test(module):
    # cols have stack depths
    # rows have len(sys.modules)

    def print_line(h, *vals):
        if not h:
            print("%5s" % h, *["%6i" % v for v in vals])
        else:
            print("%5s" % h, *["%6.1f" % v for v in vals])

    def add_modules(n):
        import random
        import sys
        for _ in range(n):
            sys.modules[f"foo_{random.randint(0,2**64)}"] = module

    def measure(depth):
        import inspect
        import timeit

        def nest(level):
            if level > 0:
                return nest(level-1)
            else:
                dur = timeit.timeit(lambda: inspect.stack(), number=1)
                return dur * 1000

        return nest(depth)

    import sys
    print_line("", *[2**e for e in range(7)])
    for i in range(1, 5):
        add_modules(n=10**i)
        times = [measure(depth=2**e) for e in range(7)]
        print_line(len(sys.modules), *times)

python 3.11.0a7+ optimized build ====

# sys has no __file__ and doesn't enter getmodule cache
>>> import sys
>>> run_test(sys)
           1      2      4      8     16     32     64
   87    2.1    0.8    1.0    1.3    2.0    3.3    6.1
  187    2.0    2.5    2.7    3.6    5.5    9.5   16.8
 1187   13.6   15.7   19.1   26.3   39.6   67.4  123.3
11187  134.1  150.3  183.4  252.0  383.5  750.3 1189.8
>>> exit()

>>> import random
>>> run_test(random)
           1      2      4      8     16     32     64
   87    2.1    0.7    0.9    1.2    1.7    2.9    5.6
  187    2.3    1.1    1.5    1.8    2.5    4.3    7.8
 1187   17.0    4.3    5.6    7.1   11.1   18.6   33.9
11187  164.6   37.4   45.7   61.6   94.7  161.0  297.7
>>> exit()

Tables show time in milliseconds for a single inspect.stack() call.
Rows show len(sys.modules)
Columns indicate stack depth

Your environment

  • CPython versions tested on: 3.9, 3.11.0a7+
  • Operating system and architecture: MacOS, Linux, x64

Metadata

Metadata

Assignees

No one assigned

    Labels

    3.12only security fixesperformancePerformance or resource usagestdlibPython modules in the Lib dirtype-bugAn unexpected behavior, bug, or error

    Projects

    No projects

    Milestone

    No milestone

    Relationships

    None yet

    Development

    No branches or pull requests

    Issue actions