[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
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
Paolo
[Prev in Thread] |
Current Thread |
[Next in Thread] |
- Re: [Qemu-trivial] [PATCH 0/7] remove useless muldiv64(),
Paolo Bonzini <=