Measure loading times of QGIS projects

Question

For QGIS there is already a method to measure loading times of plugins ( qgis.utils.plugin_times):

How to tell which QGIS plugins are slow to load?

Is there something similar to measure loading times of the parts of q QGIS-project (layers, composer ...)?

I found something in the cpp part (qgsbench.cpp) https://github.com/qgis/QGIS/blob/530397c1683cc787ef90bc27e2d958779ed0d754/tests/bench/qgsbench.cpp so perhaps there is also a way to get things measured with python/pyqgis.

Answer 1

An answer for QGIS 3.16 (did not test on previous versions)

You have 3 possibles groups in profiler at the moment in QGIS (startup, projectload, render). You should be aware now, there is a widget with the profiler content (cf screenshot)

To get current used list of group, do QgsApplication.profiler().groups()

To get time for all existing measurements (default or your own)

profiler = QgsApplication.profiler()
for group in profiler.groups():
    translatedGroupName = profiler.translateGroupName(group)
    for child in profiler.childGroups('', group):
        value = profiler.profileTime(child, group)
        childGroup = profiler.childGroups(child, group)
        # group = name in the GUI combobox but human friendly
        # child = name of the first column
        # Time for execution
        print(translatedGroupName, child, value)
        if len(childGroup) > 0:
            for subGroup in childGroup:
                print(subGroup, profiler.profileTime(subGroup, group))
        
# Weird thing here = order when looping differs from the one in the GUI...

# For global time per group, in theory, you should do the following 
# but does not work (return 0.0)
# Instead, you may sum values in the loop above to get "right" total time
for group in profiler.groups():
    print(group, profiler.totalTime(group))

If you want your own measures with your own group

from time import sleep
profiler = QgsApplication.profiler()

profiler.start('your task name 1', 'your new group name')
# To simulate waiting time but normally, you run your custom code
sleep(11.0)
profiler.end('your new group name')

profiler.start('your task name 2', 'your new group name')
# To simulate waiting time but normally, you run your custom code
sleep(8.0)
profiler.end('your new group name')

# Alternate way to avoid start and end using Python context
# Drawback: you can't log in your own group but only in startup group (default)
with QgsRuntimeProfiler.profile('qwerty'):
    sleep(2)
    # Do something