linux-kernel - Re: [RFC][PATCH] printk: increase devkmsg write() ratelimit

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Date:   Tue, 18 Dec 2018 11:48:12 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Borislav Petkov <bp@...en8.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [RFC][PATCH] printk: increase devkmsg write() ratelimit

On Tue, Dec 18, 2018 at 06:18:42PM +0900, Sergey Senozhatsky wrote:
> 	Hello,
> 	
> 	RFC
> 
> A painful subject:
> 
> I just noticed that stock systemd (no systemd debugging enabled) on my
> x86 box write()-s during shutdown to devkmsg more than before, so old
> devkmsg ratelimits do not apply:
> 
> $ sudo journalctl -n 40000 -f | grep "kernel: printk: systemd-shutdow"
>  kernel: printk: systemd-shutdow: 35 output lines suppressed due to ratelimiting
>  kernel: printk: systemd-shutdow: 31 output lines suppressed due to ratelimiting
>  kernel: printk: systemd-shutdow: 35 output lines suppressed due to ratelimiting
>  kernel: printk: systemd-shutdow: 36 output lines suppressed due to ratelimiting
>  kernel: printk: systemd-shutdow: 36 output lines suppressed due to ratelimiting
>  kernel: printk: systemd-shutdow: 36 output lines suppressed due to ratelimiting
>  kernel: printk: systemd-shutdow: 36 output lines suppressed due to ratelimiting
>  kernel: printk: systemd-shutdow: 35 output lines suppressed due to ratelimiting
> 
> I know that there is a "kernel.printk_devkmsg" interface; do we
> expect every systemd-enabled distro to find that out and to tweak
> kernel.printk_devkmsg or shall we change the default devkmsg
> ratelimit instead?

How about we complain to systemd instead?