New issue 2111: sys.settrace with a local function is about 40x slower than the
same function at the top level
https://bitbucket.org/pypy/pypy/issues/2111/syssettrace-with-a-local-function-is-about
David MacIver:
The following code demonstrates the issue. A trivial tracing function which
does nothing doesn't cause much of a slow down when defined at the top level,
but when the same function is defined locally it takes much much longer:
```
#!python
import sys
import random
import time
def hash_str(s):
h = 0
for c in s:
h = (h * 31 + ord(c)) & (2 ** 64 - 1)
return h
random.seed(1)
data = [
hex(random.getrandbits(1024)) for _ in range(500)
]
def trace_global(frame, event, arg):
return trace_global
def trace_and_hash_global(d):
sys.settrace(trace_global)
hash_str(d)
sys.settrace(None)
def trace_and_hash_local(d):
def trace_local(frame, event, arg):
return trace_local
sys.settrace(trace_local)
hash_str(d)
sys.settrace(None)
if __name__ == '__main__':
for ex in [trace_and_hash_global, trace_and_hash_local]:
start = time.time()
for d in data:
ex(d)
print(ex.__name__, time.time() - start)
```
For me this prints:
```
('trace_and_hash_global', 0.07121396064758301)
('trace_and_hash_local', 2.784956932067871)
```
This is running on pypy 2.6.0 on linux.
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