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From: John Ogness <john.ogness@linutronix.de>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH next v3 07/15] printk: introduce CONSOLE_LOG_MAX for improved multi-line support
Date: Tue, 02 Mar 2021 15:34:49 +0100	[thread overview]
Message-ID: <87h7ltpqt2.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <CAMuHMdWCM4MLkwRZTZU2Sne3gEvjBT9gowLUKLJbTAYh5gb1wg@mail.gmail.com>

Hi Geert,

On 2021-03-02, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Tue, Mar 2, 2021 at 2:54 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>> On Thu, Feb 25, 2021 at 9:30 PM John Ogness <john.ogness@linutronix.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@linutronix.de>
>>> Reviewed-by: Petr Mladek <pmladek@suse.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).

Petr was concerned that this patch might raise issues for the small
devices.

>> Who is printing such long lines to the console?

Some printk users like to print large multi-line messages into a single
record. They can get pretty long. But since no one is complaining with
the current 1024, we can assume it is big enough.

For v4 I will return it back to 1024 bytes.

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

Yes. Although once we move to threaded printers, I don't think anyone
will care. Also, I think the netconsole will become quite attractive
when we move to threaded printers.

John Ogness

  reply	other threads:[~2021-03-02 19:48 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-25 20:24 [PATCH next v3 00/15] printk: remove logbuf_lock John Ogness
2021-02-25 20:24 ` John Ogness
2021-02-25 20:24 ` John Ogness
2021-02-25 20:24 ` John Ogness
2021-02-25 20:24 ` [PATCH next v3 01/15] um: synchronize kmsg_dumper John Ogness
2021-02-25 20:24   ` John Ogness
2021-03-01 16:16   ` Petr Mladek
2021-03-01 16:16     ` Petr Mladek
2021-03-01 16:57     ` Petr Mladek
2021-03-01 16:57       ` Petr Mladek
2021-03-02  8:06       ` John Ogness
2021-03-02  8:06         ` John Ogness
2021-03-02 10:12         ` Petr Mladek
2021-03-02 10:12           ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 02/15] mtd: mtdoops: " John Ogness
2021-02-25 20:24   ` John Ogness
2021-03-01 12:13   ` Petr Mladek
2021-03-01 12:13     ` Petr Mladek
2021-03-02 10:45     ` John Ogness
2021-03-02 10:45       ` John Ogness
2021-03-02 12:48       ` Petr Mladek
2021-03-02 12:48         ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 03/15] printk: limit second loop of syslog_print_all John Ogness
2021-02-25 20:24 ` [PATCH next v3 04/15] printk: kmsg_dump: remove unused fields John Ogness
2021-02-25 20:24 ` [PATCH next v3 05/15] printk: refactor kmsg_dump_get_buffer() John Ogness
2021-02-25 20:24 ` [PATCH next v3 06/15] printk: consolidate kmsg_dump_get_buffer/syslog_print_all code John Ogness
2021-02-25 20:24 ` [PATCH next v3 07/15] printk: introduce CONSOLE_LOG_MAX for improved multi-line support John Ogness
2021-03-02 13:54   ` Geert Uytterhoeven
2021-03-02 13:58     ` Geert Uytterhoeven
2021-03-02 14:34       ` John Ogness [this message]
2021-02-25 20:24 ` [PATCH next v3 08/15] printk: use seqcount_latch for clear_seq John Ogness
2021-02-25 20:24 ` [PATCH next v3 09/15] printk: use atomic64_t for devkmsg_user.seq John Ogness
2021-02-25 20:24 ` [PATCH next v3 10/15] printk: add syslog_lock John Ogness
2021-03-01 17:07   ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 11/15] printk: kmsg_dumper: remove @active field John Ogness
2021-02-25 20:24   ` John Ogness
2021-03-01 17:09   ` Petr Mladek
2021-03-01 17:09     ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 12/15] printk: introduce a kmsg_dump iterator John Ogness
2021-02-25 20:24   ` John Ogness
2021-02-25 20:24   ` John Ogness
2021-02-25 20:24   ` John Ogness
2021-02-25 21:59   ` Kees Cook
2021-02-25 21:59     ` Kees Cook
2021-02-25 21:59     ` Kees Cook
2021-02-26  2:57   ` kernel test robot
2021-02-26  7:59   ` John Ogness
2021-02-26  7:59     ` John Ogness
2021-02-26  7:59     ` John Ogness
2021-02-26  7:59     ` John Ogness
2021-02-26  7:59     ` John Ogness
2021-03-01 18:07   ` Petr Mladek
2021-03-01 18:07     ` Petr Mladek
2021-03-01 18:07     ` Petr Mladek
2021-03-01 18:07     ` Petr Mladek
2021-03-02 13:20     ` John Ogness
2021-03-02 13:20       ` John Ogness
2021-03-02 13:20       ` John Ogness
2021-03-02 13:55       ` Petr Mladek
2021-03-02 13:55         ` Petr Mladek
2021-03-02 13:55         ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 13/15] printk: remove logbuf_lock John Ogness
2021-03-02 12:15   ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 14/15] printk: kmsg_dump: remove _nolock() variants John Ogness
2021-02-25 20:24   ` John Ogness
2021-02-25 20:24 ` [PATCH next v3 15/15] printk: console: remove unnecessary safe buffer usage John Ogness

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