Linux CPU PSI helper

psitool_cpu.py

#!/usr/bin/env python3

from hashlib import sha256
from pickle import load, dump
from socket import gethostname
from time import time


def current_psi_dict():
    with open('/proc/pressure/cpu', 'r') as psifile:
        total = psifile.read().split(' ')[4].split('=')[1]
        return {
            'value': int(total),
            'time': int(time())
        }


def write_current_value(temp_file):
    current_value = current_psi_dict()
    with open(temp_file, 'wb') as valuefile:
        dump(current_value, valuefile)


def get_last_value(name):
    result = False
    with open(name, 'rb') as valuefile:
        result = load(valuefile)

    return result


def get_filename():
    hash = sha256(gethostname().encode('utf-8')).hexdigest()[:8]
    return '/tmp/{}_psi'.format(hash)


def get_difference(temp_file):
    last_value = get_last_value(temp_file)
    if last_value is False:
        return "-1"
    current_value = current_psi_dict()
    time_difference = current_value['time'] - last_value['time']
    value_difference = current_value['value'] - last_value['value']
    if time_difference == 0:
        # Prevent division by zero, feed last one
        return current_value['value']
    return(int(value_difference / time_difference))


def main():

    temp_file = get_filename()

    try:
        with open(temp_file) as f:
            print(get_difference(temp_file))
    except IOError:
        print('-1')
    finally:
        write_current_value(temp_file)


main()