Messages in this thread | | | Date | Tue, 10 Apr 2001 05:31:05 -0700 | From | David Schleef <> | Subject | Re: No 100 HZ timer ! |
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On Tue, Apr 10, 2001 at 02:04:17PM +0200, Mikulas Patocka wrote: > > Adding and removing timers happens much more frequently than PIT tick, so > comparing these times is pointless. > > If you have some device and timer protecting it from lockup on buggy > hardware, you actually > > send request to device > add timer > > receive interrupt and read reply > remove timer > > With the curent timer semantics, the cost of add timer and del timer is > nearly zero. If you had to reprogram the PIT on each request and reply, it > would slow things down. > > 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.
dave...
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