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From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Petr Mladek <pmladek@suse.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
Subject: Re: [RFC PATCH v1 08/25] printk: add ring buffer and kthread
Date: Tue, 12 Mar 2019 18:58:56 +0900	[thread overview]
Message-ID: <20190312095856.GA426@jagdpanzerIV> (raw)
In-Reply-To: <87va0pznsq.fsf@linutronix.de>

On (03/11/19 11:51), John Ogness wrote:
> > In new printk design the tasks are still affected by printing floods.
> > Tasks have to line up and (busy) wait for each other, regardless of
> > contexts.
> 
> They only line up and busy wait is to add the informational message to
> the ring buffer. The current printk implementation is the same in this
> respect. And as you've noted, the logbuf spinlock is not a source of
> latencies.

I was talking about prb_lock().

> > When I do ./a.out --loglevel=X  I have a clear understanding that
> > all messages which fall into [critical, X] range will be in the logs,
> > because I told that application that those messages are important to
> > me right now. And it used to be the same with the kernel loglevel.
> 
> The loglevel is not related to logging. It specifies the amount of
> console printing. But I will assume you are referring to creating log
> files by having an external device store the console printing.

Right. E.g. screenlog.0

> > But now the kernel will do its own thing:
> >
> >   - what the kernel considers important will go into the logs
> >   - what the kernel doesn't consider important _maybe_ will end up
> >     in the logs (preemptible printk kthread). And this is where
> >     loglevel now. After the _maybe_ part.
> 
> "what the kernel considers" is a configuration option of the
> administrator. The administrator can increase the verbocity of the
> console (loglevel) without having negative effects on the system
> itself. Also, if the system were to suddenly crash, those crash messages
> shouldn't be in jeopardy just because the verbocity of the console was
> turned up.

Right. I'm not very sure about yet another knob which everyone
should figure out. I guess I won't be surprised to find out that
people set it to loglevel value.

	-ss

  reply	other threads:[~2019-03-12  9:59 UTC|newest]

Thread overview: 149+ 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 [this message]
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 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
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
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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