[pypy-dev] performance problems with Krakatau

[Maciej Fijalkowski]

Hi Robert.

This is going to be a long mail, so bear with me :)

The first take away is that pypy warmup is atrocious (that's
unimpressive, but you might be delighted to hear I'm working on it
right now, except I'm writing this mail). It's quite a bit of work, so
it might or might not make it to the next pypy release. We also don't
know how well it'll work.

The runs that I have now, when running 3 times in the same process
look like this (this includes other improvements mentioned later):

46s 32s 29s (cpython takes always 29s)

Now, this is far from ideal and we're working on making it better (in
fact it's a very useful benchmark), but I can pinpoint some stuff that
we will fix and some stuff we won't fix in the near future. One thing
that I've already fixed today is loops over tuple when doing x in
tuple (so tuple.__contains__).

One of the problems with this code is that I don't think it's very
efficient. While that's not a good reason to be slower than cpython,
it gives you an upper bound on what can be optimized away. Example
(from java/structuring.py):

new = new if old is None else tuple(x for x in old if x in new)

now note that this has a complexity of O(n^2), because you're
iterating for all of the one tuple and then for each over all of the
elements of the other tuple.

Another example:

return [x for x in zip(*map(self._doms.get, nodes)) if len(set(x))==1][-1][0]

this creates quite a few lists, while all it wants to do is to grab
the last one.

Those tiny loops are found a bit everywhere. I think more consistent
data structures will make it a lot faster on both CPython and PyPy.

>From our side, we'll improve generator iterators today and warmup some
time in the not-so-near future.

Speaking of which - memory consumptions is absolutely atrocious. It's
a combination of JIT using too much memory, generator iterators not
being cleaned correctly *and* some bug that prevents JIT loops from
being freed. we'll deal with all of it, give us some time (that said,
the memory consumption *will* be bigger than cpython, but hopefully by
not that much).

I'm sorry I can't help you as much as I wanted

Cheers,
fijal


On Thu, Jan 16, 2014 at 10:50 AM, Maciej Fijalkowski <fijall at gmail.com> wrote:
> On Wed, Jan 15, 2014 at 7:20 PM, Robert Grosse <n210241048576 at gmail.com> wrote:
>> Oh sorry, I forgot about that.
>>
>> You need to find the rt.jar from your Java installation and pass the path on
>> the command line. For example, if it's located in C:\Program
>> Files\Java\jre7\lib, you could do
>> python -i Krakatau\decompile.py -out temp asm-debug-all-4.1.jar -path
>> "C:\Program Files\Java\jre7\lib\rt.jar"
>> Obviously on Linux it will be somewhere else. It shouldn't really matter
>> which version of Java you have since the standard library is pretty stable..
>
> Thanks, I'm looking into it. Would you mind if we add Krakatau as a
> benchmark for our nightlies?