Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Fri, 7 Feb 2020 09:49:02 +0100 | Subject | Re: [for-next][PATCH 04/26] bootconfig: Add Extra Boot Config support |
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Hi Hiramatsu-san,
On Fri, Feb 7, 2020 at 1:30 AM Masami Hiramatsu <mhiramat@kernel.org> wrote: > On Thu, 6 Feb 2020 18:20:15 +0100 > Geert Uytterhoeven <geert@linux-m68k.org> wrote: > > On Thu, Feb 6, 2020 at 3:42 PM Masami Hiramatsu <mhiramat@kernel.org> wrote: > > > On Thu, 6 Feb 2020 12:54:05 +0100 > > > Borislav Petkov <bp@alien8.de> wrote: > > > > On Tue, Jan 14, 2020 at 04:03:20PM -0500, Steven Rostedt wrote: > > > > > diff --git a/init/Kconfig b/init/Kconfig > > > > > index a34064a031a5..63450d3bbf12 100644 > > > > > --- a/init/Kconfig > > > > > +++ b/init/Kconfig > > > > > @@ -1215,6 +1215,17 @@ source "usr/Kconfig" > > > > > > > > > > endif > > > > > > > > > > +config BOOT_CONFIG > > > > > + bool "Boot config support" > > > > > + select LIBXBC > > > > > + default y > > > > > > > > Any particular reason this is default y? Why should it be enabled by > > > > default on all boxes? > > > > > > Oh, you are not the first person asked that :) > > > > > > https://lkml.org/lkml/2019/12/9/563 > > > > > > And yes, I think this is important that will useful for most developers > > > and admins. Since the bootconfig already covers kernel and init options, > > > this can be a new standard way to pass args to kernel boot. > > > > > > And as I reported above thread, the memory footpoint of view, most code > > > and working memory are released after boot. Also, as Linus's suggested, > > > now this feature is enabled only if user gives "bootconfig" on the kernel > > > command line. So the side effect is minimized. > > > > With m68k/atari_defconfig, bloat-o-meter says: > > > > add/remove: 39/0 grow/shrink: 2/0 up/down: 13086/0 (13086) > > > > which is IMHO not that small for a "default y" option that may or may not > > be used. > > > > Especially: > > > > Function old new delta > > xbc_nodes - 8192 +8192 > > > > Any chance xbc_nodes can be allocated dynamically, and only when needed? > > Yes, I think we can use memblock to allocate it. However, this xbc_nodes is
Good.
> __init_data, which is released right after boot. So I think it should be > OK except for your system doesn't have user space...
__initdata is still part of the kernel image (note that we no longer have __initbss) and consumes RAM early on, and is thus subject to e.g. bootloader[1] and platform limitations (e.g. the kernel must fit in the first block of physical memory). So trying to avoid large static arrays is useful.
> > Yes, there are industrial products running Linux on a current ARM SoC > > using the builtin 8 or 10 MiB of SRAM (+ XIP for the kernel), so these > > definitely want to say CONFIG_BOOT_CONFIG=n. > > I think for such products the kernel must be tuned with custom config, > and you can say CONFIG_BOOT_CONFIG=n. That is a configurable feature.
I do not dispute that.
[1] Re: [PATCH] dma-debug: dynamic allocation of hash table https://lore.kernel.org/lkml/CAMuHMdVSyD62nvRmN-v6CbJ2UyqH=d7xdVeCD8_X5us+mvCXUQ@mail.gmail.com/
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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
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