linux-kernel - Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup

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Message-ID: <20180111053507.GD494@jagdpanzerIV>
Date:   Thu, 11 Jan 2018 14:35:07 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Tejun Heo <tj@...nel.org>, Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        Cong Wang <xiyou.wangcong@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jan Kara <jack@...e.cz>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        rostedt@...e.goodmis.org, Byungchul Park <byungchul.park@....com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Pavel Machek <pavel@....cz>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup

On (01/10/18 14:17), Steven Rostedt wrote:
[..]
> OK, lets start over.

good.

> Right now my focus is an incremental approach. I'm not trying to solve
> all issues that printk has. I've focused on a single issue, and that is
> that printk is unbounded. Coming from a Real Time background, I find
> that is a big problem. I hate unbounded algorithms.

agreed! so why not bound it to watchdog threshold then? why bound
it to a random O(logbuf) thing? which is not even constant. when you
un-register or disable one or several consoles then call_console_drivers()
becomes faster; when you register/enable consoles then the entire
call_console_drivers() becomes slower. how do we build a reliable
algorithm on that O(logbuf)?

	-ss