linux-kernel - Re: [PATCH v2 00/12] arm64: Kconfig: Update ARCH

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Date:   Fri, 1 Oct 2021 13:59:45 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Olof Johansson <olof@...om.net>
Cc:     Saravana Kannan <saravanak@...gle.com>,
        Will McVicker <willmcvicker@...gle.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Lee Jones <lee.jones@...aro.org>,
        "Cc: Android Kernel" <kernel-team@...roid.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-rtc@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2 00/12] arm64: Kconfig: Update ARCH_EXYNOS select configs

Hi Olof,

On Fri, Oct 1, 2021 at 7:36 AM Olof Johansson <olof@...om.net> wrote:
> A much more valuable approach would be to work towards being able to
> free up memory by un-probed drivers at the end of boot. That would
> possibly benefit all platforms on all architectures.

We used to have such a functionality in arch/ppc (not arch/powerpc!),
where code/data could be tagged __prep, __chrp, or __pmac, to put it
in a special section, and to be freed with initdata when unused.  It
was removed in v2.6.15[1], as the savings weren't worth the hassle.
In a more fragmented space like arm the memory lost due to alignment
of the sections would be even more substantial.

Another problem is to know when is the end of the boot, especially
with deferred probing.

[1] 6c45ab992e4299c8 ("[PATCH] powerpc: Remove section free() and
linker script bits")

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds