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  • Committer: Bazaar Package Importer
  • Author(s): Rick Clark
  • Date: 2008-09-08 16:35:57 UTC
  • mfrom: (1.1.1 upstream)
  • Revision ID: james.westby@ubuntu.com-20080908163557-l3ixzj5dxz37wnw2
Tags: 1.0.18-0ubuntu1
New upstream release 

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