Load the IRQ file and update the internal dict.

def __update(self):
        """Load the IRQ file and update the internal dict."""
        self.reset()

        if not os.path.exists(self.IRQ_FILE):
            # Correct issue #947: IRQ file do not exist on OpenVZ container
            return self.stats

        try:
            with open(self.IRQ_FILE) as irq_proc:
                time_since_update = getTimeSinceLastUpdate('irq')
                # Read the header
                self.__header(irq_proc.readline())
                # Read the rest of the lines (one line per IRQ)
                for line in irq_proc.readlines():
                    irq_line = self.__humanname(line)
                    current_irqs = self.__sum(line)
                    irq_rate = int(
                        current_irqs - self.lasts.get(irq_line)
                        if self.lasts.get(irq_line)
                        else 0 // time_since_update)
                    irq_current = {
                        'irq_line': irq_line,
                        'irq_rate': irq_rate,
                        'key': self.get_key(),
                        'time_since_update': time_since_update
                    }
                    self.stats.append(irq_current)
                    self.lasts[irq_line] = current_irqs
        except (OSError, IOError):
            pass

        return self.stats