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

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 1/11/07 21:14, "Dave Winchell" <dwinchell@xxxxxxxxxxxxxxx> wrote:

> 1. Increase missed ticks threshold to 100 seconds. Per the comment in
> the patch,

I assume that's the magic number 100000 in the patch? I think removing the
check entirely would be better than an arbitrarily high threshold that we're
baiscally hoping will never trigger.

> 3.  Call pt_process_missed_ticks() unconditionally and place the
>     test for no_missed_tick_accounting inside pt_process_missed_ticks().
>     This returns the calculation for the next timer expiration
>     to the original method. The original method is important
>     as it sets up a theoretical time space at t=0 where expirations
>     occur only at n*period, where n is any integer. This, in turn, removes
>     rounding errors.

Why do 'rounding errors' matter? I thought that no_missed_tick_accounting
was for guests which sampled the TSC on tick interrupt and used that to
determine elapsed wall time, in which case why would it matter when exactly
the tick interrupt is delivered?

 -- Keir



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