Re: No 100 HZ timer !

Mikulas Patocka
2001-04-10T14:11:26Z

> > Note that you call mod_timer also on each packet received - and in worst
> > case (which may happen), you end up reprogramming the PIT on each packet.
>
> This just indicates that the interface needs to be richer -- i.e.,
> such as having a "lazy timer" that means: "wake me up when _at least_
> N ns have elapsed, but there's no hurry." If waking you up at N ns
> is expensive, then the wakeup is delayed until something else
> interesting happens.
>
> This is effectively what we have now anyway. Perhaps the
> current add_timer() should be mapped to lazy timers.

BTW. Why we need to redesign timers at all? The cost of timer interrupt
each 1/100 second is nearly zero (1000 instances on S/390 VM is not common
case - it is not reasonable to degradate performance of timers because of
this).

Timers more precise than 100HZ aren't probably needed - as MIN_RTO is 0.2s
and MIN_DELACK is 0.04s, TCP would hardly benefit from them.

Mikulas