### 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.type = 's'
        self.width = 17
        self.scale = 0
        self.vars = ('latency process',)
        self.pid = str(os.getpid())
        self.pidset1 = {}; self.pidset2 = {}

    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.val['result'] = 0
        self.val['process'] = ''
        for pid in os.listdir('/proc/'):
            try:
                ### Is it a pid ?
                int(pid)

                ### Filter out dstat
                if pid == self.pid: continue

                ### Reset values
                if not self.pidset1.has_key(pid):
                    self.pidset1[pid] = {'wait_ticks': 0}

                ### Extract name
                name = open('/proc/%s/stat' % pid).read().split()[1][1:-1]

                ### Extract counters
                l = open('/proc/%s/schedstat' % pid).read().split()

            except ValueError:
                continue
            except IOError:
                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:
            for pid in self.pidset2.keys():
                self.pidset1[pid].update(self.pidset2[pid])

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

        ### Debug (show PID)
#       self.val['latency process'] = '%*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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