Ok, I've looked at this more closely now and I believe I have a fix. I've also
discovered that changes in the DLR make this much better as well in the 2.1
branch. But the numbers I get are:
2.0: 59.9065353243
2.1: 4.28863087116
2.1 + dict fixes: 1.22241745833
These numbers are quite dependent upon the number of types that have been seen
for hashing and equality. In 2.0 increasing the number of types will cause the
long running loop to become progressively worse. In 2.1 we're smart enough to
re-organize the L2 cache based upon the most recently used items which makes
this much faster. W/ my changes the dictionaries are smarter about managing
call sites based upon their type of keys.
My guess is we can add my dictionary fix to 2.0 but back porting all of the
call site changes might be too much.
Here's my repro:
import System
class x(object):
pass
data = [1, 1.0, 1L, 1.0, 'abc', 1L, frozenset(), xrange(2), frozenset(),
BaseException(), ord, type, True, x(), System.Collections.ArrayList(),
System.Collections.Hashtable(), System, KeyError('x'), AttributeError('foo'),
Warning(), 1L]
d = {}
for i in data:
d[i] = 0
i in d
del d[i]
import time
start = time.clock()
data = data[-5:]
x = {}
for i in xrange(100000):
for val in data:
x[val] = 0
val in x
del x[val]
end = time.clock()
print end - start
From: [email protected]
[mailto:[email protected]] On Behalf Of Dino Viehland
Sent: Tuesday, January 06, 2009 11:25 AM
To: [email protected]; Discussion of IronPython
Subject: Re: [IronPython] Weird performance issue
I think we are thrashing the hash code call site in
CommonDictionaryStorage.HashSite._HashSite. Alternately it could be the equals
call site in PythonContext._equalRetBoolSite. Similar to the property issue
you can look at the call site object and see if it's going to the fixed
read-only EmptyRuleSet.
We can probably add 2 sites which are per-dictionary but we might need to do
something more clever as that could regress general dictionary perf.
The DLR team is going to be looking into general issues with understanding
what's going on with call sites. Yesterday I pointed out performance
investigations as being something important for them to look at.
From: [email protected]
[mailto:[email protected]] On Behalf Of Glenn Jones
Sent: Tuesday, January 06, 2009 6:07 AM
To: Discussion of IronPython
Subject: [IronPython] Weird performance issue
Hi all,
More from the Resolver One upgrade:
We are seeing several performance failures in our tests, which we expect
because the performance profile of IPy2 is different to IPy1. There is one that
is perplexing and we hope that someone can give us some insight into possible
causes for us to investigate.
One of our performance tests only fails when it is preceded by other tests.
There is (as far as we can tell) no shared state between the tests. After much
poking around, we discovered that replacing a set with a list caused the
performance to improve from ~700ms down to ~100ms. We have been unable get a
minimal repro, so far. Here's a little more detail on the how the code works:
class Thing(object):
def run(arg1, arg2):
* do some stuff
s = set()
* do stuff that populates s
return list(s)
We create a Thing and call run so that the set contains an entry, if we then
create a new Thing and call the run method it takes 10 times longer than
expected.
If we change s = set to s = [] (and convert s.add to s.append, where
appropriate), and do the same as above, the second call to run behaves as we
expect. There is (at least in our code) nothing shared between the first call
to run and the second call.
Does anyone have any ideas about where we can look to work out what's
happening? Any suggestions for ways to diagnose this?
Thanks
Glenn & Kamil
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