linux-kernel - Re: kernel losing printk messages?

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Date:	Tue, 26 Feb 2008 22:59:07 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Szekeres István <szekeres@....hu>
cc:	linux-kernel@...r.kernel.org
Subject: Re: kernel losing printk messages?

On Tue, 26 Feb 2008, Szekeres István wrote:

> >  I guess in dmesg the output is also corrupted, right?
> Interesting. Even after a dmesg -c -s 1000000 it contains only the end
> of the story. This is the beginning of the dmesg output:

Probably your kernel ring buffer is too small (log_buf_len boot 
parameter).

> rusalka:~% dmesg | head
> input.c: Mapping: Consumer.0230 ---> IGNORED
> [85080.775297] drivers/hid/hid-input.c: Mapping: Consumer.0231 ---> IGNORED
> [85080.775302] drivers/hid/hid-input.c: Mapping: Consumer.0232 ---> IGNORED
> [85080.775308] drivers/hid/hid-input.c: Mapping: Consumer.0233 ---> Key.ScrollUp
> [85080.775314] drivers/hid/hid-input.c: Mapping: Consumer.0234 --->
> Key.ScrollDown
> So the first line is corrupted. 

It is very probably just because it didn't fit into the ring buffer.

> In the remaining of the output (total=220 lines) I cannot see the 
> evidence of corruption.

So the corruption you see in your /var/log is probably just userspace 
issue (syslogd/klogd not grabbing lines coming too fast for too long?). 
Still, it seems to work for me here.

Thanks,

-- 
Jiri Kosina
SUSE Labs