linux-kernel - Re: [PATCH v4] printk: Add console owner and waiter logic to loadbalance console writes

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Message-Id: <201711091922.IHJ81787.OVQFFJOSOLtHMF@I-love.SAKURA.ne.jp>
Date:   Thu, 9 Nov 2017 19:22:58 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     mhocko@...nel.org, rostedt@...dmis.org
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        linux-mm@...ck.org, xiyou.wangcong@...il.com,
        dave.hansen@...el.com, hannes@...xchg.org, mgorman@...e.de,
        pmladek@...e.com, sergey.senozhatsky@...il.com, vbabka@...e.cz,
        peterz@...radead.org, torvalds@...ux-foundation.org, jack@...e.cz,
        mathieu.desnoyers@...icios.com, rostedt@...e.goodmis.org
Subject: Re: [PATCH v4] printk: Add console owner and waiter logic to loadbalance console writes

Michal Hocko wrote:
> Hi,
> assuming that this passes warn stall torturing by Tetsuo, do you think
> we can drop http://lkml.kernel.org/r/1509017339-4802-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
> from the mmotm tree?

I don't think so.

The rule that "do not try to printk() faster than the kernel can write to
consoles" will remain no matter how printk() changes. Unless asynchronous
approach like https://lwn.net/Articles/723447/ is used, I think we can't
obtain useful information.