linux-kernel - Re: [PATCH next v3 07/15] printk: introduce CONSOLE_LOG

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Date:   Tue, 2 Mar 2021 14:58:28 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH next v3 07/15] printk: introduce CONSOLE_LOG_MAX for
 improved multi-line support

Hi John,

On Tue, Mar 2, 2021 at 2:54 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Thu, Feb 25, 2021 at 9:30 PM John Ogness <john.ogness@...utronix.de> wrote:
> > Instead of using "LOG_LINE_MAX + PREFIX_MAX" for temporary buffer
> > sizes, introduce CONSOLE_LOG_MAX. This represents the maximum size
> > that is allowed to be printed to the console for a single record.
> >
> > Rather than setting CONSOLE_LOG_MAX to "LOG_LINE_MAX + PREFIX_MAX"
> > (1024), increase it to 4096. With a larger buffer size, multi-line
> > records that are nearly LOG_LINE_MAX in length will have a better
> > chance of being fully printed. (When formatting a record for the
> > console, each line of a multi-line record is prepended with a copy
> > of the prefix.)
> >
> > Signed-off-by: John Ogness <john.ogness@...utronix.de>
> > Reviewed-by: Petr Mladek <pmladek@...e.com>
>
> Thanks for your patch!
>
> This increases kernel size by more than 3 KiB, which affects small
> devices (e.g. SoCs with 10 MiB of SRAM inside).
> Who is printing such long lines to the console?

BTW, printing a single line of 1024 characters to a serial console at
115200 bps takes almost 100 ms.

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