Re: [patch 1/3] kmsg: Kernel message catalog macros.

From: "Tim Hockin" <thockin@hockin.org>
To: "Pavel Machek" <pavel@suse.cz>
Cc: "Jan Blunck" <jblunck@suse.de>, "Greg KH" <gregkh@suse.de>,
	"Joe Perches" <joe@perches.com>,
	schwidefsky@de.ibm.com, linux-kernel@vger.kernel.org,
	linux-s390@vger.kernel.org,
	lf_kernel_messages@lists.linux-foundation.org,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Michael Holzheu" <holzheu@de.ibm.com>,
	"Gerrit Huizenga" <gh@us.ibm.com>,
	"Randy Dunlap" <randy.dunlap@oracle.com>,
	"Jan Kara" <jack@suse.cz>, "Sam Ravnborg" <sam@ravnborg.org>,
	"Jochen Voß" <jochen.voss@googlemail.com>,
	"Kunai Takashi" <kunai@linux-foundation.jp>,
	"Tim Bird" <tim.bird@am.sony.com>
Subject: Re: [patch 1/3] kmsg: Kernel message catalog macros.
Date: Mon, 18 Aug 2008 10:51:34 -0700	[thread overview]
Message-ID: <b3ece790808181051v1dc1ff81yc5b46348d59ab491@mail.gmail.com> (raw)
In-Reply-To: <20080818092317.GD6635@atrey.karlin.mff.cuni.cz>

On Mon, Aug 18, 2008 at 2:23 AM, Pavel Machek <pavel@suse.cz> wrote:
> Hi!
>
>> > I don't think that he wants to unify all the printk's in the system. I don't
>> > think that reporting all errors "in the same way as an ATA error" makes any
>> > sense. That would just lead to very stupid and unnatural messages for all
>> > errors that are not like "ATA errors". Annotation of existing errors is a much
>> > more flexible and feasible solution to that problem.
>>
>> Please don't misinterpret.  I don't want to make other errors parse
>> like an ATA error, I want to make the plumbing be parallel.  I want
>> one umbrella mechanism for reporting things that are more important
>> than just-another-printk().
>>
>> Because frankly, "parse dmesg" is a pretty crappy way to have to
>> monitor your system for failures, and I am tired of explaining to
>> people why we still do that.
>
> "parse dmesg" does not work for monitoring your system for failures;
> dmesg buffer can overflow.
>
> If something fails, you should get errno returned for userspace, and
> that's where you should be doing the monitoring.
>
> So... what parts don't return enough information to userspace so that
> you need to parse dmesg? Lets fix them.

If I get a DMA timeout on my disk, I want to know about it.  If I get
an OOM kill, I want to know about it.  Etc.

I *don't* want every application to participate in system monitoring,
and that's what it seems you're suggesting.  I want a monitoring
daemon which is notified of important system events.  We like to
report these things in various ways, including squirting them out onto
the network.

I *don't* want to run regexes against dmesg or /var/log/messages or
/var/log/kernel every N seconds, that's just a gross hack.  I really
want first-class notifications of significant events.  I don't mind
having to do parsing of events - as I said before, they can even be
loosely structured strings.  They just need to be more important than
a plain old printk(), and preferably come through a different channel.

I understand that many users will not want this level of monitoring,
and that's why it should be flexible enough to devolve into printk().
But we have thousands of systems.  I need a better view of what is
happening.

Tim