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

From: Paolo Bonzini
Subject: Re: [Qemu-trivial] [PATCH 0/7] remove useless muldiv64()
Date: Tue, 25 Aug 2015 18:51:08 -0400 (EDT)

> 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: address@hidden


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