Tachyon flamegraph: Total time displayed is affected by sampling rate

[JostMigenda]

Bug report

Bug description:

As discussed with @pablogsal during EuroPython sprints:

The hover views in Tachyon’s flamegraph format show incorrect values for the total time. Using this simple example script (flamegraph_demo.py):

import time

def main():
    f_1()
    f_2()

def f_1():
    time.sleep(0.5)

def f_2():
    time.sleep(1)

main()

python -m profiling.sampling run --flamegraph --browser flamegraph_demo.py

generates the following output:

The time displayed in the sidebar is correct; but hovering over the flamegraph shows an incorrect “Total time”.

Additional notes:

• The total time displayed is proportional to the sampling rate; e.g., when running with -r 10kHz (instead of the default 1kHz above), the “Total time” is displayed as 15 ms instead of 1.50 ms.
• This issue is specific to the --flamegraph output format; using --gecko gives correct values.
• All tested in 3.15.0b4.

CPython versions tested on:

3.15

Operating systems tested on:

macOS

Linked PRs

• gh-154059: Fix Tachyon flame graph time units #154036