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Differential D402

util: make nogc effective for CPython
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Authored by quark on Aug 15 2017, 1:33 AM.

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rHG05264fc9d8d6: util: make nogc effective for CPython
Summary

279cd80059d4 made util.nogc a no-op. It was to optimize PyPy. But it slows
down CPython if many objects (like 300k+) are created.

For example, running hg log -r . without extensions in hg-committed with
14k+ obsmarkers have the following times:

before        | after
hg    | chg   | hg    | chg
-----------------------------
1.262 | 0.860 | 1.077 | 0.619 (seconds, best of 20 runs)

Therefore let's re-enable nogc for CPython.

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quark created this revision.Aug 15 2017, 1:33 AM
Closed by commit rHG05264fc9d8d6: util: make nogc effective for CPython (authored by quark). · Explain WhyAug 15 2017, 3:42 AM
This revision was automatically updated to reflect the committed changes.

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Mmercurial/util.py (9 lines)

Diff 909

mercurial/util.py

Python's garbage collector triggers a GC each time a certain number of Python's garbage collector triggers a GC each time a certain number of
container objects (the number being defined by gc.get_threshold()) are container objects (the number being defined by gc.get_threshold()) are
allocated even when marked not to be tracked by the collector. Tracking has allocated even when marked not to be tracked by the collector. Tracking has
no effect on when GCs are triggered, only on what objects the GC looks no effect on when GCs are triggered, only on what objects the GC looks
into. As a workaround, disable GC while building complex (huge) into. As a workaround, disable GC while building complex (huge)
containers. containers.
This garbage collector issue have been fixed in 2.7. This garbage collector issue have been fixed in 2.7. But it still affect
CPython's performance.
""" """
if sys.version_info >= (2, 7):
return func
def wrapper(*args, **kwargs): def wrapper(*args, **kwargs):
gcenabled = gc.isenabled() gcenabled = gc.isenabled()
gc.disable() gc.disable()
try: try:
return func(*args, **kwargs) return func(*args, **kwargs)
finally: finally:
if gcenabled: if gcenabled:
gc.enable() gc.enable()
return wrapper return wrapper
if pycompat.ispypy:
# PyPy runs slower with gc disabled
nogc = lambda x: x
def pathto(root, n1, n2): def pathto(root, n1, n2):
'''return the relative path from one place to another. '''return the relative path from one place to another.
root should use os.sep to separate directories root should use os.sep to separate directories
n1 should use os.sep to separate directories n1 should use os.sep to separate directories
n2 should use "/" to separate directories n2 should use "/" to separate directories
returns an os.sep-separated path. returns an os.sep-separated path.
If n1 is a relative path, it's assumed it's If n1 is a relative path, it's assumed it's