Vmprof: "Undefined" in flamegraph, and "No stack trace has been recorded (profile is empty)!"

[shhovhan]

Hello all,
Its seems that last changes and udpates on vmprof were in 2019, but I hope someone will help me to setup vmprof for my project. Here are the problems:
I have installed vmprof client and server and when I run vmprof

1. by API like this:

             with open('logs/vmprof.log', 'w+b') as fd:
                vmprof.enable(fd.fileno())
                ..... some code here.....
                ..... some code here.....
                ..... some code here.....
                vmprof.disable()

it creates vmprof.log file as expected. then I upload it to my local server and as a result I see lot of "undefined" in flamegraph.

QUESTION: What to do with this undefineds. How to solve this problem?
2. I want to enable and disable profiling by a signal. For that I use SIGUSR signal custom handler: here is the code:

    gevent.signal(signal.SIGUSR1, self.sigusr1_handler)
    def sigusr1_handler(self):
        if not vmprof.is_enabled():
            with open('logs/vmprof.log', 'w+b') as fd:
                vmprof.enable(fd.fileno())
        else:
            vmprof.disable()

it creates vmprof log, but when I try to open on server there were nothing, infinite loading and preloader. I have tried to see if it works with vmprofshow but I got this message:

WARNING: The profiling completed in less than 1 seconds. Please run your programs longer!
No stack trace has been recorded (profile is empty)!

QUESTION: How to solve this problem? Is it possible to enable or disable vmprof by signal?

[shhovhan]

UPDATES:
In 2nd case vmprof.log is not empty. Logging information written in file. I can find there all known function names that you can see in flamegraph above.
I use Python 2.7, pypy 6.0, vmprof 0.4.15, 0.4.13, 0.4.12