Re: [PATCH] lib/int_sqrt.c: optimize for small argument values

From: Peter Zijlstra
Date: Fri Oct 20 2017 - 12:22:48 EST


On Fri, Oct 20, 2017 at 07:18:51AM -0700, Kees Cook wrote:
> On Thu, Oct 19, 2017 at 11:13 PM, Joe Perches <joe@xxxxxxxxxxx> wrote:
> > On Thu, 2017-10-19 at 13:31 -0700, Michael Davidson wrote:
> >> int_sqrt() currently takes approximately constant time
> >> regardless of the value of the argument. By using the
> >> magnitude of the operand to set the initial conditions
> >> for the calculation the cost becomes proportional to
> >> log2 of the argument with the worst case behavior not
> >> being measurably slower than it currently is.
> >
> > https://lkml.org/lkml/2017/7/24/408
>
> Ah! Cool. I don't see this version queued up for -next. Where does
> Peter's version stand?

Oh, crud, forgot all about it. I'd have to double check I addressed the
concerns Linus had with my Changelogs, but other than that he seemed to
be OK.