From: Andrew Morton <akpm@linux-foundation.org>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
linux-kernel@vger.kernel.org, Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH v2] minmax: clamp more efficiently by avoiding extra comparison
Date: Fri, 23 Sep 2022 15:54:12 -0700 [thread overview]
Message-ID: <20220923155412.b0132fc62eca18817a023cd2@linux-foundation.org> (raw)
In-Reply-To: <20220923154001.4074849-1-Jason@zx2c4.com>
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?
next prev parent reply other threads:[~2022-09-23 22:54 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-23 10:06 [PATCH] " Jason A. Donenfeld
2022-09-23 10:35 ` Andy Shevchenko
2022-09-23 10:40 ` Jason A. Donenfeld
2022-09-23 10:48 ` Jason A. Donenfeld
2022-09-23 15:12 ` Andy Shevchenko
2022-09-23 15:13 ` Jason A. Donenfeld
2022-09-23 15:40 ` [PATCH v2] " Jason A. Donenfeld
2022-09-23 16:41 ` Kees Cook
2022-09-23 16:42 ` Jason A. Donenfeld
2022-09-23 16:53 ` Andy Shevchenko
2022-09-23 16:54 ` Jason A. Donenfeld
2022-09-23 19:47 ` Kees Cook
2022-09-23 22:54 ` Andrew Morton [this message]
2022-09-24 0:02 ` Kees Cook
2022-09-24 10:37 ` Jason A. Donenfeld
2022-09-25 16:29 ` Andrew Morton
2022-09-26 10:00 ` Andy Shevchenko
2022-09-26 12:23 ` Jason A. Donenfeld
2022-09-26 13:34 ` [PATCH v3 1/2] minmax: sanity check constant bounds when clamping Jason A. Donenfeld
2022-09-26 13:34 ` [PATCH v3 2/2] minmax: clamp more efficiently by avoiding extra comparison Jason A. Donenfeld
2022-09-26 18:30 ` Kees Cook
2022-09-26 21:33 ` Jason A. Donenfeld
2022-09-26 13:46 ` [PATCH v3 1/2] minmax: sanity check constant bounds when clamping Andy Shevchenko
2022-09-26 18:26 ` Kees Cook
2022-10-04 13:41 ` Jason A. Donenfeld
2022-10-04 14:39 ` Kees Cook
2022-10-04 15:01 ` Jason A. Donenfeld
2022-09-26 18:30 ` [PATCH v2] minmax: clamp more efficiently by avoiding extra comparison Kees Cook
2022-09-23 15:10 ` [PATCH] " Andy Shevchenko
2022-09-23 15:11 ` Jason A. Donenfeld
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