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

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Date:   Tue, 18 Dec 2018 18:47:23 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] printk: increase devkmsg write() ratelimit

On Wed, Dec 19, 2018 at 01:52:17AM +0900, Sergey Senozhatsky wrote:
> But devkmsg ratelimits systemd errors, so one does not even know that
> "some debugging is required". For instance from my x86 box:
> 
>  Unmounting /home...
>  [..]
>  home.mount: Mount process exited, code=exited status=32
>  Failed unmounting /home.
> 
> I don't want to debug systemd, I want to know that something didn't
> work out. 10 messages max and 5 seconds interval looks a bit too strict.

So how much is not strict?

And what happens if you raise that ratelimiting level and the *one* line
which is most important for debugging an issue, still doesn't get logged
because all of a sudden, doofus is more talkative, overflows the new
limit and we drop the important line?

All I'm saying is, gradually raising the limit is the wrong approach
- there will always be a case where something important doesn't get
logged.

What we need is a different solution, maybe what Rostedt proposes or
so...

-- 
Regards/Gruss,
    Boris.

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