Cannot Allocate Memory when using Interrupts

[alindsay81]

So i created a fairly simple python program counting pulses using interrupts and i tested it on the bench with a single input for a couple of days and everything seemed to work well, when i started to use it for real i had 5 inputs and the pulse frequency was a bit higher, after around 22 hours the counting would stop. When i looked into why it could see that Python3 memory use was going up and up everytime a pulse was counted. The first thing i did was to create a test program that only counted and the problem persists with the pi eventually giving the error Cannot Allocate Memory - my test code is here;

def testcount(event):
global Count1
Count1 += 1
print(Count1)

Setup the Digital IO to watch for Rising Edge only

pifacedigital = pifacedigitalio.PiFaceDigital()

listener = pifacedigitalio.InputEventListener(chip=pifacedigital)
listener.register(0, pifacedigitalio.IODIR_RISING_EDGE, testcount)
listener.activate()

Here is a screen shot of the pi back on the bench showing the memory use rising. it only rises when a pulse is received

[mpruessmeier]

Hello alindsay81,

i am in a big projekt and had the same problems. the threading of pfacedigitalio is broken in pifacecommon. if you activate the listeners like you do, every event/interrupt is caching memory, this is a "i think known" memory leak.

I tried to find the leak, but could not find it.

this is my workaround:

import pifacedigitalio as pf
import time
import threading

in_tic = [ 0, 0, 0, 0, 0, 0, 0, 0]

Handle holen vom PiFace

pifacedigital = pf.PiFaceDigital()

Tic_in Klasse wird initialisiert

class Tic_in(threading.Thread):

def __init__(self):
    threading.Thread.__init__(self)

def run(self):
    global pifacedigital
    global in_tic
    print("Start on hearing:")

    tic_old = [0,0,0,0,0,0,0,0]
    tic_new = [0,0,0,0,0,0,0,0]
    x=0
    #loop im deamon
    while True:
       tic_new[x]=pifacedigital.input_pins[x].value
       if tic_new[x] and not tic_old[x]:
          in_tic[x] += 1
       tic_old[x] = tic_new[x]
       x+=1
       if x>7: 
          x=0
          time.sleep(0.000001)

#Then start the thread

tic_in = Tic_in()
tic_in.deamon = True
tic_in.start()

this is much faster and the memory leak is gone.
I hope this will work for you.

Greetings from germany, Marc

[alindsay81]

Hi Marc, Thanks so much for this - With a few small changes it slots perfectly with the rest of my project and works exactly as it should! - CPU use was very high (85%) so i increased the sleep time to 10ms and cpu use came down to 35% - my pulse width is 50ms so 10ms cycle time is no problem for me

[tompreston]

Hm, I'll flag this for investigation in pifacecommon. Thanks.