Viewing file:  jiffies.py (1.58 KB) -rw-r--r--
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import os
def detect_jiffies():
"""Returns the number of jiffies per second for this machine.
A jiffy is a value used by the kernel to report certain time-based
events. Jiffies occur N times per second where N varies depending
on the hardware the kernel is running on. This function gets the
uptime for the current process, forks a child process and gets the
uptime again; finally, using the running time of the child process
compared with the uptimes to determine number of jiffies per
second.
"""
uptime1_file = open("/proc/uptime")
uptime2_file = open("/proc/uptime")
read_uptime1 = uptime1_file.read
read_uptime2 = uptime2_file.read
while True:
uptime1_data = read_uptime1()
# Fork a process and exit immediately; this results in the
# child process being left around as a zombie until waitpid()
# is called.
pid = os.fork()
if pid == 0:
os._exit(0)
uptime2_data = read_uptime2()
stat_file = open("/proc/%d/stat" % pid)
stat_data = stat_file.read()
stat_file.close()
os.waitpid(pid, 0)
seconds_uptime1 = float(uptime1_data.split()[0])
seconds_uptime2 = float(uptime2_data.split()[0])
jiffie_uptime = int(stat_data.split()[21])
jiffies1 = int(jiffie_uptime/seconds_uptime1+0.5)
jiffies2 = int(jiffie_uptime/seconds_uptime2+0.5)
if jiffies1 == jiffies2:
break
uptime1_file.seek(0)
uptime2_file.seek(0)
uptime1_file.close()
uptime2_file.close()
return jiffies1
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