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: / usr / share / dstat /
Filename : dstat_top_latency.py
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### Authority: Dag Wieers <dag$wieers,com>

class dstat_plugin(dstat):
    """
    Top process with highest total latency.

    Displays name and total amount of CPU time waited in milliseconds of
    the process that has the highest total amount waited for the measured
    timeframe.

    For more information see:

        http://eaglet.rain.com/rick/linux/schedstat/
    """

    def __init__(self):
        self.name = 'highest total'
        self.vars = ('latency process',)
        self.type = 's'
        self.width = 17
        self.scale = 0
        self.pidset1 = {}

    def check(self):
        if not os.access('/proc/self/schedstat', os.R_OK):
            raise Exception, 'Kernel has no scheduler statistics, use at least 2.6.12'

    def extract(self):
        self.output = ''
        self.pidset2 = {}
        self.val['result'] = 0
        for pid in proc_pidlist():
            try:
                ### Reset values
                if not self.pidset1.has_key(pid):
                    self.pidset1[pid] = {'wait_ticks': 0}

                ### Extract name
                name = proc_splitline('/proc/%s/stat' % pid)[1][1:-1]

                ### Extract counters
                l = proc_splitline('/proc/%s/schedstat' % pid)
            except IOError:
                continue
            except IndexError:
                continue

            if len(l) != 3: continue

            self.pidset2[pid] = {'wait_ticks': long(l[1])}

            totwait = (self.pidset2[pid]['wait_ticks'] - self.pidset1[pid]['wait_ticks']) * 1.0 / elapsed

            ### Get the process that spends the most jiffies
            if totwait > self.val['result']:
                self.val['result'] = totwait
                self.val['pid'] = pid
                self.val['name'] = getnamebypid(pid, name)

        if step == op.delay:
            self.pidset1 = self.pidset2

        if self.val['result'] != 0.0:
            self.output = '%-*s%s' % (self.width-4, self.val['name'][0:self.width-4], cprint(self.val['result'], 'd', 4, 100))

        ### Debug (show PID)
#       self.output = '%*s %-*s' % (5, self.val['pid'], self.width-6, self.val['name'])

    def showcsv(self):
        return '%s / %.4f' % (self.val['name'], self.val['result'])

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