On Wed, Nov 16, 2011 at 1:23 PM, Robert Collins
<robert.coll...@canonical.com> wrote:
> So, I'd like to capture a backtrace whenever we make a SQL query or
> HTTP service call.
...
I misread timeits python API. Unlike the command line it doesn't
normalise - so you need to divide by your main loop count.
Wgrant points out that 20 frames is too shallow due to TAL.
So, here is an updated simulation:60 frames, and repeats normalised
out (you can change 'number =xxx' to any value, and the results should
stay pretty constant.
The updated timing is:
0.25 seconds for 1000 backtraces at 60 frames deep. Or 0.25ms per
backtrace. This is less than the overhead caused by a page cache miss
on the DB server, so I'm going to grab them all.
:!./backtracetiming.py
0.251479740143
0.000343389511108
tb time: 0.251136350632
-Rob
#!/usr/bin/env python
import timeit
# This generates a 20 deep stackframe, and then calls a function that makes a
# stack trace, 1000 times - to simulate a deep appserver stack + oops capturing
# and formating tracebacks.
code = """import traceback
oops = []
def stackframe(depth=60):
l = locals()
for i in range(10):
l[str(i)] = i
if depth:
stackframe(depth-1)
else:
for i in range(1000):
oops.append(''.join(traceback.format_stack()))
stackframe()
"""
code2 = """import traceback
oops = []
def stackframe(depth=60):
l = locals()
for i in range(10):
l[str(i)] = i
if depth:
stackframe(depth-1)
else:
for i in range(1000):
oops.append('')
stackframe()
"""
# Time with tracebacks
number = 100
t = timeit.Timer(code)
times = t.repeat(number=number)
best_with = min(times) / float(number)
print best_with
# Time without
t = timeit.Timer(code2)
times = t.repeat(number=number)
best_without = min(times) / float(number)
print best_without
print "tb time:", best_with - best_without
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