Re: [Qemu-devel] [PATCH] qemu-timer: remove unnecessary code

[Cao jin]

On 07/13/2016 06:21 PM, Paolo Bonzini wrote:
> On 13/07/2016 11:06, Cao jin wrote:
> > When passed argument 'ns' is 0, macro DIV_ROUND_UP will return 0 also.
>
> It's potentially slower though.

Is it because the function in the i/o loop path, so the potentially 
extra arithmetical instructions matters?

> Paolo
>
> > Cc: Paolo Bonzini <address@hidden>
> > Signed-off-by: Cao jin <address@hidden>
> > ---
> >   qemu-timer.c | 6 +-----
> >   1 file changed, 1 insertion(+), 5 deletions(-)
> >
> > diff --git a/qemu-timer.c b/qemu-timer.c
> > index eb22e92..cfe0893 100644
> > --- a/qemu-timer.c
> > +++ b/qemu-timer.c
> > @@ -285,12 +285,8 @@ int qemu_timeout_ns_to_ms(int64_t ns)
> >           return -1;
> >       }
> >
> > -    if (!ns) {
> > -        return 0;
> > -    }
> > -
> >       /* Always round up, because it's better to wait too long than to wait too
> > -     * little and effectively busy-wait
> > +     * short and effectively busy-wait
> >        */
> >       ms = DIV_ROUND_UP(ns, SCALE_MS);

--
Yours Sincerely,

Cao jin