Hi Makoto,
currently sys._getframe() is mostly killing the jit
since it currently needs access to all frame objects,
if i remember correct (arigo, fijal or anto will know for sure),
the jit currently just bails out if it gets a sys._getframe call
(which easyly explain the ~34 times slower in your test)
i think there are ways to support it,
but i currently don't have the time/knowledge to check which of them work
-- Ronny
On 05/27/2012 06:24 AM, Makoto Kuwata wrote:
Hi,
I found that sys._getframe() (or sys._getframe().f_locals) is
very slow in PyPy 1.8.
For example, the following takes only 0.0398 sec on PyPy 1.8:
def f5(x): return f4(x)
def f4(x): return f3(x)
def f2(x): return f1(x)
def f1(x): reutrn None ## just return None
for _ in xrange(1000000):
f5(0)
But the next one takes 1.3563 sec.
def f5(x): return f4(x)
def f4(x): return f3(x)
def f2(x): return f1(x)
def f1(x): reutrn sys._getframe(1) ## calls sys._getframe(1)
for _ in xrange(1000000):
f5(0)
Is there any plan to make it faster in the future release?
Background
----------
I'm an author of Tenjin, a high-speed template engine for Python.
Tenjin supports PyPy officially, and I received a report that
there are some cases in which Tenjin is very slow on PyPy.
I investigated report and found that it is the sys._getframe()
and sys._getframe().f_locals that makes Tenjin much slow on PyPy.
Tenjin uses sys._getframe(1).f_locals in order to access to
caller's local variables. It is necessary for Tenjin.
Benchmark
---------
Here is a benchmark script to measure cost of sys._getframe(1)
and sys._getframe(1).f_locals.
(You must install Benchmarker library to run it.)
https://gist.github.com/2802160
Benchmark result shows that:
* Cost of sys._getframe(1) and sys._getframe(1).f_locals is
not so much on CPython but very big on PyPy.
* Nested depth os function call affects to cost of them.
For example:
def f5(x): return f4(x)
def f4(x): return f3(x)
def f2(x): return f1(x)
def f1(x): reutrn sys._getframe(1)
f5(0)
is much slower than:
def f2(x): return f1(x)
def f1(x): reutrn sys._getframe(1)
f2(0)
By the way, PyPy is awesome.
It is not only faster than CPython but also has high-level
compatibility with CPython. Almost of all test script of Tenjin
works on PyPy. Great.
I hope Tenjin works much faster on PyPy.
--
regards,
makoto kuwata
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