Re: [Qemu-devel] [PATCH 0/7] remove useless muldiv64()

[Paolo Bonzini <pbonzini@redhat.com>]

> Originally, timers were ticks based, and it made sense to
> add ticks to current time to know when to trigger an alarm.
> 
> But since commit:
> 
> 7447545 change all other clock references to use nanosecond resolution
> accessors
> 
> All timers use nanoseconds and we need to convert ticks to nanoseconds, by
> doing something like:
> 
>      y = muldiv64(x, get_ticks_per_sec(), TIMER_FREQ)
> 
> where x is the number of device ticks and y the number of system ticks.
> 
> y is used as nanoseconds in timer functions,
> it works because 1 tick is 1 nanosecond.
> (get_ticks_per_sec() is 10^9)
> 
> But if get_ticks_per_sec() / TIMER_FREQ is an integer, we can do:
> 
>     y = x * TIMER_PERIOD;

Cc: qemu-trivial@nongnu.org

Paolo