[arch-general] Fedora Speeds Up Python 3.

Chris Billington chrisjbillington at gmail.com
Tue Nov 26 15:28:52 UTC 2019

Oh I remember why I didn't override libpython functions with LD_PRELOAD.
Python is statically linked to libpython in Ubuntu, which I was using at
the time, so it didn't work. Fedora decided not to go that far, but yeah,
Ubuntu has already taken that plunge.

If LD_PRELOADing libpython doesn't work in Ubuntu, then there probably
aren't many projects using it.

On Tue, Nov 26, 2019 at 9:31 AM Chris Billington <chrisjbillington at gmail.com>

> Ah, that's interesting.
> I thought that would break my GIL profiling project that uses LD_PRELOAD
> (shameless plug: https://github.com/chrisjbillington/gil_load), but since
> I think I'm only overriding libc functions, it should be fine.
> I'm sure there are other things it will break (I could have overridden
> libpython functions instead - I wonder why I didn't, it seems simpler but
> there was probably a reason), but if someone wants to use code that hacks
> on the interpreter itself, having to install a custom python to do so is
> not so unreasonable. Those speedups are nothing to scoff at.
> -Chris
> On Tue, Nov 26, 2019 at 5:07 AM Ralph Corderoy <ralph at inputplus.co.uk>
> wrote:
>> Hi,
>> I thought this might be of interest.
>> https://fedoraproject.org/wiki/Changes/PythonNoSemanticInterpositionSpeedup
>> By building with -fno-semantic-interposition they remove the PLT that
>> provides a level of indirection when calling a libpython function.
>> libpython often calls itself and the PLT adds L1-cache pressure plus
>> prevents inlining.  Gives gains of 25% on some workloads.
>> --
>> Cheers, Ralph.

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