Python 3 in Yocto very slow on Raspberry Pi

Question

We've used Python 2 for an embedded application that we're currently prototyping on Raspberry Pi. It's been a bit slow, but acceptable.

Now we've ported the application to Python 3. But for some reason the application runs about 4 times slower than with Python 2! I was expecting Python 3 to be a bit slower, but nothing like this!

Our Linux distribution is based on Yocto 2.2 Morty and we are using the default Python 3.5.2 recipe with no customizations. We are also using the meta-raspberrypi layer for Raspberry compatibility.

I tried to time "pip3 --help" and got the following result:

$ time pip3 --help >/dev/null

real    0m22.686s
user    0m22.210s
sys     0m0.420s

Then I tried the same test on the same hardware (same sd card as well) using the latest Raspbian distro:

$ time pip3 --help >/dev/null

real    0m6.874s
user    0m6.530s
sys     0m0.310s

$ time pip --help >/dev/null

real    0m4.329s
user    0m4.000s
sys     0m0.300s

Python 2 pip is a little bit faster than Python 3, but the most important thing is that pip3 runs more than 3 times faster on Raspbian than on Yocto!

The tests are very repeatable, so they are not caused by pyc-generation or caching or something like that.

Any ideas how to get Yocto as fast as Raspbian?

Update:

There was some discussions about different versions of Python and Pip in Raspbian vs Yocto below, so I made a new benchmark using only Python standard libraries:

Yocto 2.2 Morty:

sh-4.3# time python3 --version
Python 3.5.2

real    0m0.024s
user    0m0.010s
sys     0m0.000s
sh-4.3# time python3 -c "import asyncio"

real    0m3.439s
user    0m3.300s
sys     0m0.110s

Raspbian:

pi@raspberrypi:~$ time python3 --version
Python 3.4.2

real    0m0.020s
user    0m0.000s
sys     0m0.010s
pi@raspberrypi:~$ time python3 -c "import asyncio"

real    0m2.023s
user    0m1.850s
sys     0m0.160s

I then downloaded Python 3.5.2 on Raspbian and built it from source, with no custom configuration (./configure; make; make install). With Python 3.5.2 I get the following result:

pi@raspberrypi:~$ time python3.5 --version
Python 3.5.2

real    0m0.018s
user    0m0.000s
sys     0m0.010s
pi@raspberrypi:~$ time python3.5 -c "import asyncio"

real    0m2.689s
user    0m2.610s
sys     0m0.070s

So it seems that Python 3.5 is considerably slower than 3.4, but still much, much slower on a default Yocto build than on Raspbian with the default build configuration.

Update 2:

I built Python 3.5.2 the same way on my Yocto system ("./configure; make; make install") and got about 20% improvement compared to the standard Python recipe:

root@la:/var/src/Python-3.5.2# time python3.5 -c "import asyncio"

real    0m2.914s
user    0m2.750s
sys     0m0.130s

Answer 1

Yocto Python 2 is compiled in optimized mode. Try configuring Python 3 (3.5.3+ I think) with ./configure --enable-optimizations as also discussed here.