linux-kernel - Re: [PATCH 0/4] Section alignment issues?

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Message-ID: <ZYIKmQj0H1YAJWlz@bombadil.infradead.org>
Date: Tue, 19 Dec 2023 13:26:49 -0800
From: Luis Chamberlain <mcgrof@...nel.org>
To: deller@...nel.org
Cc: linux-kernel@...r.kernel.org, Masahiro Yamada <masahiroy@...nel.org>,
	Arnd Bergmann <arnd@...db.de>, linux-modules@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH 0/4] Section alignment issues?

On Wed, Nov 22, 2023 at 11:18:10PM +0100, deller@...nel.org wrote:
> From: Helge Deller <deller@....de>
> My questions:
> - Am I wrong with my analysis?

This would typically of course depend on the arch, but whether it helps
is what I would like to see with real numbers rather then speculation.
Howeer, I don't expect some of these are hot paths except maybe the
table lookups. So could you look at some perf stat differences
without / with alignment ? Other than bootup live patching would be
a good test case. We have selftest for modules, the script in selftests
tools/testing/selftests/kmod/kmod.sh is pretty aggressive, but the live
patching tests might be better suited.

> - What does people see on other architectures?
> - Does it make sense to add a compile- and runtime-check, like the patch below, to the kernel?

The chatty aspects really depend on the above results.

Aren't there some archs where an unaligned access would actually crash?
Why hasn't that happened?

  Luis