Re: [Xen-devel] [PATCH] Add a timer mode that disables pending missed ticks

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 8/11/07 14:43, "Dave Winchell" <dwinchell@xxxxxxxxxxxxxxx> wrote:

> I agree that this could be a problem. I have an idea that could give us full
> SYNC and eliminate the long periods without clock interrupts.
> In pt_process_missed_ticks() when missed_ticks > 0 set pt->run_timer = 1.
> In pt_save_timer():
> 
>     list_for_each_entry ( pt, head, list )
>         if(!pt->run_timer)
>              stop_timer(&pt->timer);
> 
> And in pt_timer_fn():
> 
>     pt->run_timer = 0;
> 
> So, for a guest that misses a tick, we will interrupt him once from the
> descheduled state and then leave him alone in the descheduled state.

Well, I'd rather not complicate the code if it's avoidable. I checked in a
SYNC/ASYNC combo and code simplification as changeset 16341, and it'd be
interesting to know how that fares against your suggested scheme. I suppose
as long as we're better than ntpd's tolerance it doesn't actually matter all
that much.

 -- Keir



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