[New-bugs-announce] [issue46046] I/O bound threads got to no chance to run with small CPU bound threads with new GIL

[Souvik Ghosh]

New submission from Souvik Ghosh <souvikghosh872 at gmail.com>:

According to David Beazley' talk in PyCon'2010 in Atlanta Georgia, he demonstrated about a new GIL with running CPU bound and I/O bound threads together.

He said the talk that the threads which are forced to timeout of 5ms, will have the lower priority(which is CPU bound) and the thread which suspends the GIL within 5ms will have higher priority (which is I/O bound). 

What happens in the following code is if I set args=(10000000,) (seven zero after 1) then only I/O bound runs and returns when CPU bound takes much time to execute. But if I decrease that args to args=(1000,) then I/O bound got no chance to reaquire the GIL in the meantime even though the sys.getswitchinterval() is equal to 5ms(By default). If I/O bound doesn't reacquire GIL with args=(10000,) then the time to execute to run 
only the CPU bound takes 0.42777760000035414 seconds. Thats means almost ticks 0.42777760000035414/0.005=85 (approx) times to set the priority in between the two threads. In that case if the I/O got more priority within that time, it should have returned the value within that ticks. But I didn't happen. 

import threading
from queue import Queue
from timeit import default_timer as timer
import urllib.request


q = Queue()  # Queue technique to pass returns among threads while running


def decrement(numbers):  # CPU bound
    while numbers > 0:
        numbers -= 1
        if not q.empty():
            """I added this method because this thread will run most of the time
            because it's mostly cpu bound"""
            print(numbers)
            print(q.get(block=False))
            print(timer() - start)  # It tell after when exactly I/O bound returns value after both the threads started to run


def get_data():  # I/O bound

    with urllib.request.urlopen("https://www.google.com") as dt:
        q.put(dt.read(), block=False)


if __name__ == "__main__":
    start = timer()
    t1 = threading.Thread(target=get_data)
    #t2 = threading.Thread(target=decrement, args=(10000000,)) #For this I/O responds and returns
    t2 = threading.Thread(target=decrement, args=(100000,)) # I/O doesn't responds at all
    t1.start()
    t2.start()

    t1.join()
    t2.join()
    print(timer() - start)

Look at the second code...


import threading
from queue import Queue
from timeit import default_timer as timer
import urllib.request
import sys


q = Queue()  # Queue technique to pass returns among threads while running


def decrement(numbers):  # CPU bound
    while numbers > 0:
        numbers -= 1
        if not q.empty():
            """I added this method because this thread will run most of the time
            because it's mostly cpu bound"""
            print(numbers)
            print(q.get(block=False))
            print(timer() - start)  # It tell after when exactly I/O bound returns value after both the threads started to run


def get_data():  # I/O bound

    with urllib.request.urlopen("https://www.google.com") as dt:
        q.put(dt.read(), block=False)


if __name__ == "__main__":
    sys.setswitchinterval(0.0000000000000000000000000001)
    start = timer()
    t1 = threading.Thread(target=get_data)
    #t2 = threading.Thread(target=decrement, args=(1000000,)) #I/O responds with this 
    t2 = threading.Thread(target=decrement, args=(10000,))    # I/O doesn't responds at all even with this 0.0000000000000000000000000001 seconds of threads switching interval
    t1.start()
    t2.start()

    t1.join()
    t2.join()
    print(timer() - start)

Can't we have a more better version of GIL to set I/O threads(overall) priorities even more better and not to degrade the CPU bound and better callbacks in response? Or, try to remove the GIL?

Thank you so much, great future of Python!

----------
components: Interpreter Core
files: GIL9.py
messages: 408292
nosy: souvikghosh
priority: normal
severity: normal
status: open
title: I/O bound threads got to no chance to run with small CPU bound threads with new GIL
type: performance
versions: Python 3.10
Added file: https://bugs.python.org/file50487/GIL9.py

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<https://bugs.python.org/issue46046>
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