[pypy-issue] Issue #1811: finditer() stalls PyPy 2.3.1 (pypy/pypy)

[Rui Carmo]

New issue 1811: finditer() stalls PyPy 2.3.1
https://bitbucket.org/pypy/pypy/issue/1811/finditer-stalls-pypy-231

Rui Carmo:

I've come across a significant performance hit when using PyPy 2.3.1 with Bottle ([commit](https://github.com/defnull/bottle/blob/bc312ae49d9f7f389c06db53898e5a5f7b63c93c/bottle.py#L3429)) on Linux x86_64.

In the method below ([ref](https://github.com/defnull/bottle/blob/bc312ae49d9f7f389c06db53898e5a5f7b63c93c/bottle.py#L3429)), PyPy stalls when instantiating the generator for a good three seconds according to the timestamps of the log messages I inserted, whereas stock CPython just breezes through this.

```python
    def flush_text(self):
        text = ''.join(self.text_buffer)
        del self.text_buffer[:]
        if not text: return
        parts, pos, nl = [], 0, '\\\n'+' '*self.indent
        log.debug("begin stall")
        for m in self.re_inl.finditer(text):
            log.debug("end stall")
            prefix, pos = text[pos:m.start()], m.end()
            if prefix:
                parts.append(nl.join(map(repr, prefix.splitlines(True))))
```

I suspect this is partly due to the complexity of the regexp, but it shouldn't happen. I've filed [an issue there](https://github.com/defnull/bottle/issues/638) with a `pstats` profile.