Re: [PATCH v2] minmax: clamp more efficiently by avoiding extra comparison

Andrew Morton
2022-09-23T22:54:21Z

On Fri, 23 Sep 2022 17:40:01 +0200 "Jason A. Donenfeld" <Jason@zx2c4.com> wrote:

> Currently the clamp algorithm does:
>
> if (val > hi)
> val = hi;
> if (val < lo)
> val = lo;
>
> But since hi > lo by definition, this can be made more efficient with:
>
> if (val > hi)
> val = hi;
> else if (val < lo)
> val = lo;
>
> So fix up the clamp and clamp_t functions to do this, adding the same
> argument checking as for min and min_t.
>

The patch adds 140 bytes of text to mm/memblock.o, for example.
Presumably from the additional branch. Larger text means larger cache
footprint means slower.

So where's the proof that this change gives us a more efficient kernel?