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SubjectRe: [PATCH] refperf: work around 64-bit division
On Sat, May 30, 2020 at 10:01:36AM +0200, Arnd Bergmann wrote:
> On Sat, May 30, 2020 at 5:52 AM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> > On Fri, May 29, 2020 at 10:15:51PM +0200, Arnd Bergmann wrote:
> > > strcat(buf, "Threads\tTime(ns)\n");
> > >
> > > for (exp = 0; exp < nruns; exp++) {
> > > + u64 avg;
> > > + u32 rem;
> > > +
> > > if (errexit)
> > > break;
> > > - sprintf(buf1, "%d\t%llu.%03d\n", exp + 1, result_avg[exp] / 1000, (int)(result_avg[exp] % 1000));
> > > +
> > > + avg = div_s64_rem(result_avg[exp], 1000, &rem);
> >
> > Shouldn't this be div_u64_rem? result_avg is u64.
>
> Yes, you are right. Actually that would be an important optimization
> since div_u64_rem() optimizes for constant divisors while div_s64_rem
> uses the slow path.
>
> > > + sprintf(buf1, "%d\t%llu.%03d\n", exp + 1, avg, rem);
> >
> > Would %03u be the better specifier since rem is u32?
>
> Yes, though this makes no difference in practice.
>
> Paul, should I send a fixup for these two, or do you prefer to just
> edit it in place?

I will apply it with Randy's Ack, thank you all!

Thanx, Paul

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