linux-kernel - Re: [RFC][PATCHv3 2/5] printk: introduce printing kernel thread

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Date:   Fri, 30 Jun 2017 23:10:01 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>, Jan Kara <jack@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Eric Biederman <ebiederm@...ssion.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, Pavel Machek <pavel@....cz>,
        Andreas Mohr <andi@...as.de>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCHv3 2/5] printk: introduce printing kernel thread

On (06/30/17 15:16), Petr Mladek wrote:
[..]
>
> I wonder if I could add some counter into task_struct.
> It might be configurable. I am not sure if people would
> want this enabled on production systems where the level
> of messages should be lower anyway.

I don't think it really matters which one of the tasks has issued way
too many printk()-s. it's the state of the logbuf that matters after
all. was it one task or 5 tasks, or 15 that pushed logbuf far ahead of
console_seq, we need to throttle all of new printk() calls anyway.
just because logbuf is already too far and we need to give console a
chache to catch up. so let's activate throttling based on the logbuf
state (those seq numbers).

	-ss