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From: Olof Johansson <olof@lixom.net>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Saravana Kannan <saravanak@google.com>,
	Will McVicker <willmcvicker@google.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
	Russell King <linux@armlinux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Sylwester Nawrocki <s.nawrocki@samsung.com>,
	Tomasz Figa <tomasz.figa@gmail.com>,
	Chanwoo Choi <cw00.choi@samsung.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Alessandro Zummo <a.zummo@towertech.it>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	John Stultz <john.stultz@linaro.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Lee Jones <lee.jones@linaro.org>,
	"Cc: Android Kernel" <kernel-team@android.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
	linux-clk <linux-clk@vger.kernel.org>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	linux-rtc@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v2 00/12] arm64: Kconfig: Update ARCH_EXYNOS select configs
Date: Fri, 1 Oct 2021 08:59:57 -0700	[thread overview]
Message-ID: <CAOesGMg_eA5PNzsL76xv6kDQ2QUZeCwC04BNeucfGXkFSOE=Tw@mail.gmail.com> (raw)
In-Reply-To: <CAMuHMdUkMwyA-bk7hfr7S7TE-_S9eBUxKWKmpj0rDCUvHL+fxw@mail.gmail.com>

On Fri, Oct 1, 2021 at 4:59 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Olof,
>
> On Fri, Oct 1, 2021 at 7:36 AM Olof Johansson <olof@lixom.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.

Yeah, the balance between per-platform code size and overall kernel
code size shifted over time to a point where it wasn't as meaningful
on ppc.

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

Most of this code either has a module_init() or an initcall that
actually registers the drivers and/or probes for the platform and does
the work.

This means you can have a late equivalent hook/initcall that
determines whether this path ended up being probed/used. If it wasn't,
you can then unregister and flag the corresponding memory to be freed
at the end, and would take out the heuristics and guessing on needing
to do it automatically from the code path that's doing said freeing.


-Olof

  reply	other threads:[~2021-10-01 16:00 UTC|newest]

Thread overview: 83+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-28 23:56 [PATCH v2 00/12] arm64: Kconfig: Update ARCH_EXYNOS select configs Will McVicker
2021-09-28 23:56 ` [PATCH v2 01/12] arm64: don't have ARCH_EXYNOS select EXYNOS_CHIPID Will McVicker
2021-09-29 13:58   ` (subset) " Krzysztof Kozlowski
2021-09-29 14:00   ` Krzysztof Kozlowski
2021-09-28 23:56 ` [PATCH v2 02/12] timekeeping: add API for getting timekeeping_suspended Will McVicker
2021-09-29  3:42   ` John Stultz
2021-09-29 20:01     ` Will McVicker
2021-09-29 20:46       ` John Stultz
2021-09-30 18:31         ` Will McVicker
2021-09-28 23:56 ` [PATCH v2 03/12] clk: samsung: add support for CPU clocks Will McVicker
2021-09-28 23:56 ` [PATCH v2 04/12] clk: samsung: exynos5433: update apollo and atlas clock probing Will McVicker
2021-09-28 23:56 ` [PATCH v2 05/12] clk: export __clk_lookup Will McVicker
2021-10-08  4:31   ` Stephen Boyd
2021-09-28 23:56 ` [PATCH v2 06/12] clk: samsung: modularize exynos arm64 clk drivers Will McVicker
2021-09-28 23:56 ` [PATCH v2 07/12] clk: samsung: set exynos arm64 clk driver as tristate Will McVicker
2021-09-29 13:09   ` Krzysztof Kozlowski
2021-09-28 23:56 ` [PATCH v2 08/12] pinctrl: samsung: modularize the ARM and ARM64 pinctrls Will McVicker
2021-09-29  2:01   ` Chanho Park
2021-09-28 23:56 ` [PATCH v2 09/12] pinctrl: samsung: set PINCTRL_EXYNOS and PINCTRL_SAMSUNG as tristate Will McVicker
2021-09-28 23:56 ` [PATCH v2 10/12] soc: samsung: pmu: modularize the Exynos ARMv8 PMU driver Will McVicker
2021-09-29 13:11   ` Krzysztof Kozlowski
2021-09-28 23:56 ` [PATCH v2 11/12] soc: samsung: pm_domains: modularize EXYNOS_PM_DOMAINS Will McVicker
2021-09-29 13:36   ` Krzysztof Kozlowski
2021-09-28 23:56 ` [PATCH v2 12/12] ARM: rtc: remove HAVE_S3C_RTC in favor of direct dependencies Will McVicker
2021-09-29 11:52   ` Alexandre Belloni
2021-09-29 13:02 ` [PATCH v2 00/12] arm64: Kconfig: Update ARCH_EXYNOS select configs Krzysztof Kozlowski
2021-09-29 19:48   ` Will McVicker
2021-09-30  6:14     ` Krzysztof Kozlowski
2021-09-30  9:01       ` Arnd Bergmann
2021-09-30  9:30         ` Lee Jones
2021-09-30 10:33           ` Krzysztof Kozlowski
2021-09-30 12:34             ` Lee Jones
2021-09-30 12:38               ` Krzysztof Kozlowski
2021-09-30 10:05         ` Geert Uytterhoeven
2021-09-30  9:23       ` Lee Jones
2021-09-30 10:17         ` Geert Uytterhoeven
2021-09-30 10:56           ` Lee Jones
2021-09-30 11:25             ` Geert Uytterhoeven
2021-09-30 12:08               ` Lee Jones
2021-09-30 16:09                 ` Geert Uytterhoeven
2021-09-30 10:52         ` Krzysztof Kozlowski
2021-09-30 12:32           ` Lee Jones
2021-09-30 11:01         ` Tomasz Figa
2021-09-30 11:27           ` Geert Uytterhoeven
2021-09-30 11:51           ` Lee Jones
2021-09-30 12:10             ` Tomasz Figa
2021-09-30 12:15               ` Krzysztof Kozlowski
2021-09-30 12:45               ` Lee Jones
2021-10-01  4:01               ` Christoph Hellwig
2021-10-01  4:52                 ` Saravana Kannan
2021-10-01  4:55                   ` Christoph Hellwig
2021-09-30 12:21         ` Krzysztof Kozlowski
2021-09-30 12:39           ` Lee Jones
2021-09-30 13:08             ` Krzysztof Kozlowski
2021-09-30 13:29               ` Lee Jones
2021-09-30 16:12                 ` Geert Uytterhoeven
2021-09-30 16:21                   ` Lee Jones
2021-09-30 16:26                     ` Geert Uytterhoeven
2021-09-30 18:02                       ` Will McVicker
2021-10-01  4:04             ` Christoph Hellwig
2021-10-01  4:52     ` Olof Johansson
2021-10-01  5:23       ` Saravana Kannan
2021-10-01  5:35         ` Olof Johansson
2021-10-01  5:59           ` Will McVicker
2021-10-01  8:01             ` Krzysztof Kozlowski
2021-10-01  6:02           ` Saravana Kannan
2021-10-01  6:27             ` Olof Johansson
2021-10-01  6:30               ` Olof Johansson
2021-10-01 12:00             ` Arnd Bergmann
2021-10-01 12:31               ` Lee Jones
2021-10-01 15:43                 ` Olof Johansson
2021-10-01 11:38           ` Linus Walleij
2021-10-01 11:59           ` Geert Uytterhoeven
2021-10-01 15:59             ` Olof Johansson [this message]
2021-10-01 16:51               ` Will McVicker
2021-10-01 17:15                 ` Olof Johansson
2021-10-01 17:48                   ` Will McVicker
2021-10-01  8:19         ` Geert Uytterhoeven
2021-10-01  9:00           ` Arnd Bergmann
2021-10-01 15:27             ` Olof Johansson
2021-10-01 19:26               ` Saravana Kannan
2021-10-02  1:47                 ` Tomasz Figa
2021-10-02 21:03                 ` Olof Johansson

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