pyqt5 GUI very slow to load

sharky · 04-18-2023, 02:51 PM

Working on a network at my job where I do not have admin access.

The python3 installation does not have the required modules so I install anaconda3 in an area where I have access.

Using the anaconda3 python I have all the modules I need and everything works as expected except that GUI apps are very slow to load - about 10 to 12 seconds. If I shutdown the GUI and immediately restart is loads within a second.

Also get this output when starting the GUI.

QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-<USER>'

I can set XDG_RUNTIME_DIR but it does not affect how fast the GUI starts.

I have a home PC with all the required modules included in the system python and the same GUI loads with no 10 to 12 second delay.

Is there anyway to determine the root cause of the delay?

dugan · 04-18-2023, 03:12 PM

cProfile

sharky · 04-18-2023, 04:03 PM

Wrapping cProfile around my main function and the GUI always starts relatively quickly. Logged into several machines and the behavior was consistent. I don't know what cProfile does but it makes trouble shooting this particular issue impossible because the issue cannot be duplicated with cProfile.

I could be wrong (I usually am), but I don't think the issue is with my code because the code runs perfectly on my home PC. It is only on the job network where I see the delay and it is only on a first run, subsequent runs are normal.

EDIT: Testing with cProfile and the GUI starts up normally. Removed cProfile and in the same terminal the GUI loaded slowly.

dugan · 04-18-2023, 05:09 PM

Maybe one of the dependencies is large and it's taking forever to load off a slow network share? You can easily test that by just firing up "python3" and typing in the imports.

sharky · 04-18-2023, 05:26 PM

All the imports return to the prompt immediately.

My default shell at work is tcsh. I noticed that if I switch to bash to GUI starts up immediately. By 'immediately' I mean no discernible lag at all.

UPDATE: tried bash again and it took about 5 seconds to startup. Still an improvement but the inconsistency is annoying.

UPDATE: tried the import from python prompt again and "from PyQt5 import QtGui, uic, QtCore, QtWidgets" took about 4 to 5 seconds to load.

dugan · 04-18-2023, 05:27 PM

Quote:

Originally Posted by sharky

My default shell at work is tcsh.

Working in film production?

Do an "env | sort" in both BASH and tcsh, and then diff the two.

dugan · 04-18-2023, 05:45 PM

Sounds like you have a workaround: write a BASH script to launch your Python program.

sharky · 04-18-2023, 05:55 PM

Noticed that I can start python3 and enter "from PyQt5 import QtGui, uic, QtCore, QtWidgets" and it takes several seconds to return the prompt.

I then do ctrl-D, immediately start python3, and the import returns to the prompt immediately.

What could cause that? It appears the shell remembers the module imports from the previous python session and keeps them ready. If I wait a long time, not sure how long, before starting python a second time the imports are again slow.

sharky · 04-18-2023, 05:56 PM

Quote:

Originally Posted by dugan

Sounds like you have a workaround: write a BASH script to launch your Python program.

Tried that and there was some delay. It also appears that bash periodically has some delay in starting the GUI. However, it is never as slow as tcsh.

dugan · 04-18-2023, 06:19 PM

Quote:

Originally Posted by sharky

What could cause that? It appears the shell remembers the module imports from the previous python session and keeps them ready. If I wait a long time, not sure how long, before starting python a second time the imports are again slow.

It's certainly because of caching that's done by the filesystem itself.

You know it will become slow if you wait a while. Do that, launch the interpreter with "python3 -v", and do the imports again.

dugan · 04-18-2023, 06:30 PM

The reason it loads faster in BASH than in tcsh could just be because you're testing in BASH right after testing in tcsh. Be aware of that possibility.

sharky · 04-20-2023, 01:58 PM

Noticed this morning that a command line invocation of python took a few seconds to get to the python prompt. Did ctrl-D and immediately restarted python and the prompt appears immediately.

So python itself is slow to load, and import of Qt modules, are both slow on an initial start.

Is there know way to fix this?

teckk · 04-20-2023, 02:38 PM

Code:

sysctl vm.drop_caches=3

1st load, python has to load up into RAM.

Code:

time {
    xterm -e "python && quit()"
}

real    0m2.297s
user    0m0.089s
sys     0m0.058s

2nd load with python in RAM.

Code:

time {
    xterm -e "python && quit()"
}

real    0m0.135s
user    0m0.071s
sys     0m0.021s

Code:

cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 23
model name      : Intel(R) Core(TM)2 Duo CPU     E7500  @ 2.93GHz
...

You want faster, use a source compiled into executable language like C, C++

teckk · 04-20-2023, 02:56 PM

atest.py

Code:

#!/usr/bin/python

from PyQt5.QtWidgets import QApplication
from PyQt5.QtCore import QUrl, QSizeF
from PyQt5.QtPrintSupport import QPrinter

if __name__ == "__main__":
    print (__package__)
    print (__name__)

Code:

sysctl vm.drop_caches=3

#1st
time {
    python3 ./atest.py
}
None
__main__

real    0m2.841s
user    0m0.098s
sys     0m0.083s

#2nd
time {
    python3 ./atest.py
}
None
__main__

real    0m0.114s
user    0m0.087s
sys     0m0.027s

sharky · 04-20-2023, 04:24 PM

Apparently there is no fix. I am still confused why pyqt GUIs start consistently fast on my home system.

teckk, When I get off work I will try your test on work vs home systems.

Thanks,