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From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>,
	Steven Rostedt <rostedt@goodmis.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [for-next][PATCH 04/26] bootconfig: Add Extra Boot Config support
Date: Fri, 7 Feb 2020 09:49:02 +0100	[thread overview]
Message-ID: <CAMuHMdVW74CKL-HYJS1YcK2KDew5db6TudC3O7vxk6mjmHxAvg@mail.gmail.com> (raw)
In-Reply-To: <20200207093003.93711310cfafae98bb2a62f6@kernel.org>

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

  reply	other threads:[~2020-02-07  8:49 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14 21:03 [for-next][PATCH 00/26] tracing: Updates for 5.6 Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 01/26] perf: Make struct ring_buffer less ambiguous Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 02/26] tracing: Rename trace_buffer to array_buffer Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 03/26] tracing: Make struct ring_buffer less ambiguous Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 04/26] bootconfig: Add Extra Boot Config support Steven Rostedt
2020-02-06 11:54   ` Borislav Petkov
2020-02-06 14:41     ` Masami Hiramatsu
2020-02-06 17:20       ` Geert Uytterhoeven
2020-02-07  0:30         ` Masami Hiramatsu
2020-02-07  8:49           ` Geert Uytterhoeven [this message]
2020-02-07 13:17             ` Masami Hiramatsu
2020-02-07 14:28               ` [PATCH] bootconfig: Allocate xbc_nodes array dynamically Masami Hiramatsu
2020-02-06 17:58       ` [for-next][PATCH 04/26] bootconfig: Add Extra Boot Config support Borislav Petkov
2020-02-06 18:10         ` Randy Dunlap
2020-02-06 22:39           ` Steven Rostedt
2020-02-06 22:51             ` Borislav Petkov
2020-02-07  8:59             ` Geert Uytterhoeven
2020-02-07  2:46         ` Masami Hiramatsu
2020-02-07 11:41           ` Borislav Petkov
2020-02-07 15:06             ` Masami Hiramatsu
2020-02-10 11:25               ` Borislav Petkov
2020-02-10 15:10                 ` Masami Hiramatsu
2020-02-10 17:40                   ` Borislav Petkov
2020-02-11  2:02                     ` Masami Hiramatsu
2020-02-18 13:27                       ` Borislav Petkov
2020-02-18 17:57                         ` Steven Rostedt
2020-02-18 19:38                           ` Borislav Petkov
2020-02-19  2:26                             ` Masami Hiramatsu
2020-02-19  2:26                           ` Masami Hiramatsu
2020-02-19  2:26                         ` Masami Hiramatsu
2020-02-11  9:25                     ` Geert Uytterhoeven
2020-01-14 21:03 ` [for-next][PATCH 05/26] bootconfig: Load boot config from the tail of initrd Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 06/26] tools: bootconfig: Add bootconfig command Steven Rostedt
2020-02-07 13:02   ` Michael Ellerman
2020-02-07 13:39     ` Masami Hiramatsu
2020-02-07 13:55     ` [PATCH] tools/bootconfig: Fix wrong __VA_ARGS__ usage Masami Hiramatsu
2020-02-08 11:10       ` Michael Ellerman
2020-02-09  4:09         ` Masami Hiramatsu
2020-02-09 13:05         ` [PATCH] tools/bootconfig: Suppress non-error messages Masami Hiramatsu
2020-02-10  2:06           ` Michael Ellerman
2020-02-10  7:18             ` Masami Hiramatsu
2020-02-10  9:50               ` Michael Ellerman
2020-02-10  9:50       ` [PATCH] tools/bootconfig: Fix wrong __VA_ARGS__ usage Michael Ellerman
2020-02-10 17:07         ` Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 07/26] tools: bootconfig: Add bootconfig test script Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 08/26] proc: bootconfig: Add /proc/bootconfig to show boot config list Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 09/26] init/main.c: Alloc initcall_command_line in do_initcall() and free it Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 10/26] bootconfig: init: Allow admin to use bootconfig for kernel command line Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 11/26] bootconfig: init: Allow admin to use bootconfig for init " Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 12/26] Documentation: bootconfig: Add a doc for extended boot config Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 13/26] tracing: Apply soft-disabled and filter to tracepoints printk Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 14/26] tracing: kprobes: Output kprobe event to printk buffer Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 15/26] tracing: kprobes: Register to dynevent earlier stage Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 16/26] tracing: Accept different type for synthetic event fields Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 17/26] tracing: Add NULL trace-array check in print_synth_event() Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 18/26] tracing/boot: Add boot-time tracing Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 19/26] tracing/boot: Add per-event settings Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 20/26] tracing/boot Add kprobe event support Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 21/26] tracing/boot: Add synthetic " Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 22/26] tracing/boot: Add instance node support Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 23/26] tracing/boot: Add cpu_mask option support Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 24/26] tracing/boot: Add function tracer filter options Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 25/26] Documentation: tracing: Add boot-time tracing document Steven Rostedt
2020-01-14 21:03 ` [for-next][PATCH 26/26] tracing: trigger: Replace unneeded RCU-list traversals Steven Rostedt
2020-01-14 22:11   ` Steven Rostedt

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