[pypy-dev] Speeding up zlib in standard library

[Armin Rigo]

Hi,

On Wed, Mar 14, 2012 at 03:19, Peter Cock <p.j.a.cock at googlemail.com> wrote:
> I don't know - I was assuming any buffering would be the same
> comparing PyPy 1.8 against Python 2.6 (and 3.2). That was one
> reason for my email - is binding to C relatively slow (compared to
> the rest of PyPy running pure Python)?

Not necessarily.  You get direct C calls, both from the translated
pypy and from JITted assembler code.  There are performance hits when
e.g. the C library relies on macros, but I don't think that's the case
of zlib.

Passing big strings around, on the other hand, is typically slower on
PyPy because they need to be copied between GC-managed areas and
non-GC-managed areas.  There are vague ideas on how to improve but
nothing I can summarize in two words.

At this level, for profiling, you can use valgrind.  You'll see the
time spent in zlib itself, the time spent copying big strings around,
and the time spent actually executing the JIT-generated assembler
(this ends up in "functions" with no name, just an address).


A bientôt,

Armin.