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From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Daniel Wang <wonderfly@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
	Jiri Slaby <jslaby@suse.com>, Peter Feiner <pfeiner@google.com>,
	linux-serial@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [RFC PATCH v1 15/25] printk: print history for new consoles
Date: Wed, 27 Feb 2019 11:02:53 +0100	[thread overview]
Message-ID: <874l8pft0y.fsf@linutronix.de> (raw)
In-Reply-To: <20190227090249.fzigc7r237emlg6k@pathway.suse.cz> (Petr Mladek's message of "Wed, 27 Feb 2019 10:02:49 +0100")

On 2019-02-27, Petr Mladek <pmladek@suse.com> wrote:
> I mean that your patch does the reply on a very hidden location.

Right. I understand that and I agree.

> Regarding the per-console kthread. It would make sense if
> we stop handling all consoles synchronously. For example,
> when we push messages to fast consoles immediately and
> offload the work for slow consoles.

My per-console kthread suggestion relating to fast consoles is so that
some consoles (such as netconsole, which is quite fast) could drop less
messages than a slow console (such as uart).

> Anyway, we first need to make the offload reliable enough.
> It is not acceptable to always offload all messages.
> We have been there last few years. We must keep a high
> chance to see the messages. Any warning might be important
> when it causes the system to die. Nobody knows what message
> is such an important.

You seem to be missing the point of the series. It _is_ acceptable to
offload all messages because they are being offloaded to non-emergency
consoles. If messages are lost, it sucks (and the appropriate "dropped"
messages are sent), but it isn't critical. Once we can agree to this
point, printk becomes so much easier to work with.

Emergency consoles exist for handling important messages. They will not
drop messages. They are synchronous and immediate.

>> It is not necessary. It is desired. Why should _any_ task be punished
>> with console writing? That is what the printk kthread is for.
>
> I do not know about any acceptable solution without punishing
> the tasks. But we might find a better compromise between the
> punishment and reliability.

I do not want printk to compromise. That compromise is part of the
problem. Let's partition printk to important and non-important so that
we can optimize both. _That_ is the heart of this series.

John Ogness

  reply	other threads:[~2019-02-27 10:02 UTC|newest]

Thread overview: 147+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-12 14:29 [RFC PATCH v1 00/25] printk: new implementation John Ogness
2019-02-12 14:29 ` [RFC PATCH v1 01/25] printk-rb: add printk ring buffer documentation John Ogness
2019-02-12 14:45   ` Greg Kroah-Hartman
2019-02-12 14:29 ` [RFC PATCH v1 02/25] printk-rb: add prb locking functions John Ogness
2019-02-13 15:45   ` Petr Mladek
2019-02-13 21:39     ` John Ogness
2019-02-14 10:33       ` Petr Mladek
2019-02-14 12:10         ` John Ogness
2019-02-15 10:26           ` Petr Mladek
2019-02-15 10:56             ` John Ogness
2019-03-07  2:12   ` Sergey Senozhatsky
2019-02-12 14:29 ` [RFC PATCH v1 03/25] printk-rb: define ring buffer struct and initializer John Ogness
2019-02-12 14:46   ` Greg Kroah-Hartman
2019-02-14 12:46     ` Petr Mladek
2019-02-12 14:29 ` [RFC PATCH v1 04/25] printk-rb: add writer interface John Ogness
2019-02-14 15:16   ` Petr Mladek
2019-02-14 23:36     ` John Ogness
2019-02-15  1:19       ` John Ogness
2019-02-15 13:47       ` Petr Mladek
2019-02-17  1:32         ` John Ogness
2019-02-21 13:51           ` Petr Mladek
2019-02-12 14:29 ` [RFC PATCH v1 05/25] printk-rb: add basic non-blocking reading interface John Ogness
2019-02-18 12:54   ` Petr Mladek
2019-02-19 21:44     ` John Ogness
2019-02-21 16:22       ` Petr Mladek
2019-02-12 14:29 ` [RFC PATCH v1 06/25] printk-rb: add blocking reader support John Ogness
2019-02-18 14:05   ` Petr Mladek
2019-02-19 21:47     ` John Ogness
2019-02-12 14:29 ` [RFC PATCH v1 07/25] printk-rb: add functionality required by printk John Ogness
2019-02-12 17:15   ` Linus Torvalds
2019-02-13  9:20     ` John Ogness
2019-02-18 15:59   ` Petr Mladek
2019-02-19 22:08     ` John Ogness
2019-02-22  9:58       ` Petr Mladek
2019-02-12 14:29 ` [RFC PATCH v1 08/25] printk: add ring buffer and kthread John Ogness
2019-02-12 15:47   ` Sergey Senozhatsky
2019-02-19 13:54   ` Petr Mladek
2019-03-04  7:38   ` Sergey Senozhatsky
2019-03-04 10:00     ` Sergey Senozhatsky
2019-03-04 11:07       ` Sergey Senozhatsky
2019-03-05 21:00         ` John Ogness
2019-03-06 15:57           ` Petr Mladek
2019-03-06 21:17             ` John Ogness
2019-03-06 22:22               ` John Ogness
2019-03-07  6:41                 ` Sergey Senozhatsky
2019-03-07  6:51                   ` Sergey Senozhatsky
2019-03-07 12:50               ` Petr Mladek
2019-03-07  5:15           ` Sergey Senozhatsky
2019-03-11 10:51             ` John Ogness
2019-03-12  9:58               ` Sergey Senozhatsky
2019-03-12 10:30               ` Petr Mladek
2019-03-07 12:06     ` John Ogness
2019-03-08  1:31       ` Sergey Senozhatsky
2019-03-08 10:04         ` Petr Mladek
2019-02-12 14:29 ` [RFC PATCH v1 09/25] printk: remove exclusive console hack John Ogness
2019-02-19 14:03   ` Petr Mladek
2019-02-12 14:29 ` [RFC PATCH v1 10/25] printk: redirect emit/store to new ringbuffer John Ogness
2019-02-20  9:01   ` Petr Mladek
2019-02-20 21:25     ` John Ogness
2019-02-22 14:43       ` Petr Mladek
2019-02-22 15:06         ` John Ogness
2019-02-22 15:25           ` Petr Mladek
2019-02-25 12:11       ` Petr Mladek
2019-02-25 16:41         ` John Ogness
2019-02-26  9:45           ` Petr Mladek
2019-02-12 14:29 ` [RFC PATCH v1 11/25] printk_safe: remove printk safe code John Ogness
2019-02-22 10:37   ` Petr Mladek
2019-02-22 13:38     ` John Ogness
2019-02-22 15:15       ` Petr Mladek
2019-02-12 14:29 ` [RFC PATCH v1 12/25] printk: minimize console locking implementation John Ogness
2019-02-25 13:44   ` Petr Mladek
2019-02-12 14:29 ` [RFC PATCH v1 13/25] printk: track seq per console John Ogness
2019-02-25 14:59   ` Petr Mladek
2019-02-26  8:45     ` John Ogness
2019-02-26 13:11       ` Petr Mladek
2019-02-12 14:29 ` [RFC PATCH v1 14/25] printk: do boot_delay_msec inside printk_delay John Ogness
2019-02-12 14:29 ` [RFC PATCH v1 15/25] printk: print history for new consoles John Ogness
2019-02-26 14:58   ` Petr Mladek
2019-02-26 15:22     ` John Ogness
2019-02-27  9:02       ` Petr Mladek
2019-02-27 10:02         ` John Ogness [this message]
2019-02-27 13:12           ` Petr Mladek
2019-03-04  9:24       ` Sergey Senozhatsky
2019-02-12 14:29 ` [RFC PATCH v1 16/25] printk: implement CON_PRINTBUFFER John Ogness
2019-02-26 15:38   ` Petr Mladek
2019-02-12 14:29 ` [RFC PATCH v1 17/25] printk: add processor number to output John Ogness
2019-02-13 22:29   ` John Ogness
2019-02-12 14:29 ` [RFC PATCH v1 18/25] console: add write_atomic interface John Ogness
2019-02-12 14:29 ` [RFC PATCH v1 19/25] printk: introduce emergency messages John Ogness
2019-03-07  7:30   ` Sergey Senozhatsky
2019-03-08 10:31     ` Petr Mladek
2019-03-11 12:04       ` John Ogness
2019-03-12  2:51         ` Sergey Senozhatsky
2019-03-12  2:58       ` Sergey Senozhatsky
2019-02-12 14:29 ` [RFC PATCH v1 20/25] serial: 8250: implement write_atomic John Ogness
2019-02-27  9:46   ` Petr Mladek
2019-02-27 10:32     ` John Ogness
2019-02-27 13:55       ` Petr Mladek
2019-03-08  4:05         ` John Ogness
2019-03-08  4:17           ` John Ogness
2019-03-08 10:28           ` Petr Mladek
2019-02-12 14:29 ` [RFC PATCH v1 21/25] printk: implement KERN_CONT John Ogness
2019-02-12 14:30 ` [RFC PATCH v1 22/25] printk: implement /dev/kmsg John Ogness
2019-02-12 14:30 ` [RFC PATCH v1 23/25] printk: implement syslog John Ogness
2019-02-12 14:30 ` [RFC PATCH v1 24/25] printk: implement kmsg_dump John Ogness
2019-02-12 14:30 ` [RFC PATCH v1 25/25] printk: remove unused code John Ogness
2019-03-08 14:02   ` Sebastian Andrzej Siewior
2019-03-11  2:46     ` Sergey Senozhatsky
2019-03-11  8:18       ` Sebastian Andrzej Siewior
2019-03-12  9:38         ` Petr Mladek
2019-02-13  1:31 ` [RFC PATCH v1 00/25] printk: new implementation Sergey Senozhatsky
2019-02-13 13:43   ` John Ogness
2019-03-04  6:39     ` Sergey Senozhatsky
2019-02-13  1:41 ` Sergey Senozhatsky
2019-02-13 14:15   ` John Ogness
2019-03-04  5:31     ` Sergey Senozhatsky
2019-02-13  2:55 ` Sergey Senozhatsky
2019-02-13 14:43   ` John Ogness
2019-03-04  5:23     ` Sergey Senozhatsky
2019-03-07  9:53       ` John Ogness
2019-03-08 10:00         ` Petr Mladek
2019-03-11 10:54         ` Sergey Senozhatsky
2019-03-12 12:38           ` Petr Mladek
2019-03-12 15:15             ` John Ogness
2019-03-13  2:15               ` Sergey Senozhatsky
2019-03-13  8:19                 ` John Ogness
2019-03-13  8:40                   ` Sebastian Siewior
2019-03-13  9:27                     ` Sergey Senozhatsky
2019-03-13 10:06                       ` Sergey Senozhatsky
2019-03-14  9:27                       ` Petr Mladek
2019-03-13  8:46                   ` Sergey Senozhatsky
2019-03-14  9:14               ` Petr Mladek
2019-03-14  9:35                 ` John Ogness
2019-03-13  2:00             ` Sergey Senozhatsky
2019-02-13 16:54 ` David Laight
2019-02-13 22:20   ` John Ogness
2020-01-20 23:05 ` Eugeniu Rosca
2020-01-21 23:56   ` John Ogness
2020-01-22  2:34     ` Eugeniu Rosca
2020-01-22  7:31       ` Geert Uytterhoeven
2020-01-22 16:58         ` Eugeniu Rosca
2020-01-22 19:48           ` Geert Uytterhoeven
2020-01-24 16:09             ` Eugeniu Rosca
2020-01-27 12:32               ` Petr Mladek
2020-01-27 13:45                 ` Eugeniu Rosca
2020-01-22 10:33       ` John Ogness
2020-01-24 12:13         ` Eugeniu Rosca

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