SnakeViz tries to display the full timed call tree, but the profile file doesn't have the data for it. This leads to bogus information in SnakeViz. Consider

import time


def a(t0, t1):
    c(t0)
    d(t1)
    return


def b():
    return a(1, 4)


def c(t):
    time.sleep(t)
    return


def d(t):
    time.sleep(t)
    return


if __name__ == "__main__":
    a(4, 1)
    b()

SnakeViz gives

which is wrong: c() really takes 4 seconds when called via root -> a() -> c(), and d() takes 1 second when called via root -> a() -> d(); SnakeViz shows both as 5 seconds. More timings are wrong in the above screenshot.

To work around this sort of bugs, I created tuna which gives only the information that can be deduced from the profile: