[dm-devel] [PATCH 1/2] Revert "Revert "math64: New div64_u64_rem helper""
Ingo Molnar
mingo at kernel.org
Tue Aug 20 08:09:10 UTC 2013
* Stanislaw Gruszka <sgruszka at redhat.com> wrote:
> On Fri, Aug 09, 2013 at 03:56:03PM -0400, Mike Snitzer wrote:
> > This reverts commit f3002134158092178be81339ec5a22ff80e6c308.
> >
> > div64_u64_rem was removed because there were no other users.
> >
> > But Device Mapper's I/O statistics support has a need for
> > div64_u64_rem; reintroduce this helper.
>
> This slows down div64_u64 operation, especially on 32-bit
> systems.
>
> Since dm statistic code is possibly not performance
> critical perhaps you could use something like below
> instead to calculate remainder:
>
> res = div64_u64(a, b);
> rem = a - b*res;
Or introduce a separately named helper without touching the
existing methods.
Thanks,
Ingo
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