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Date:   Tue, 17 Sep 2019 16:51:30 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To:     Petr Mladek <pmladek@suse.com>
Cc:     Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        John Ogness <john.ogness@linutronix.de>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Andrea Parri <parri.andrea@gmail.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Brendan Higgins <brendanhiggins@google.com>,
        Paul Turner <pjt@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Theodore Ts'o <tytso@mit.edu>,
        Prarit Bhargava <prarit@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: printk meeting at LPC
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On (09/16/19 12:46), Petr Mladek wrote:
> Hmm, it seems that journalctl is able to filer device specific
> information, for example, I get:
> 
> $> journalctl _KERNEL_DEVICE=+usb:2-1
> -- Logs begin at Tue 2019-08-13 09:00:03 CEST, end at Mon 2019-09-16 12:32:58 CEST. --
> Aug 13 09:00:04 linux-qszd kernel: usb 2-1: new high-speed USB device number 2 using ehci-pci
> 
> One question is if anyone is using this filtering. Simple grep is
> enough. Another question is whether it really needs to get passed
> this way.

Hmm. If I recall correctly...

There was some sort of discussion (and a patch, I believe) a long time
ago. If I'm not mistaken, guys at facebook somehow add "machine ID"
(e.g. CONFIG_DEFAULT_HOSTNAME?) to kernel messages (via dicts). This
has one interesting use case: net consoles print extended headers.

So they have monitoring systems, which capture and track net consoles
output from many servers, and should one of them warn/oom/etc. they
immediately know which one of the machines is "under the weather"
(ext_text directly points at the right server).

Well, once again, if I recall this correctly.

	-ss