linux-kernel - Re: [PATCH] printk timestamp post-boot suppression

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Date:	Wed, 27 Aug 2008 16:26:52 +0100
From:	Simon Farnsworth <simon.farnsworth@...lan.com>
To:	Joe Korty <joe.korty@...r.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] printk timestamp post-boot suppression

Joe Korty wrote:
> Suppress printk timestamping after system boot.
> 
> The timestamp printk prefix seems most useful during boot,
> where it easily shows where the boot sequence is spending
> its time.
> 
It's also very useful while the system is running. We've had problems
with systems where the HDD or libata was "hiccuping" and stalling the
entire system for 30 seconds; our logs were useless, as syslog was
timestamping with the timestamp *after* the stall ended (as that was
when it received the message), and dmesg had no timestamps.

In this case, our problem ran away and hid when we turned on printk
timestamps, but if it recurred, we'd want the timestamps available to
let us work out which operation was taking lots of time, without having
to rebuild the kernel.
-- 
Simon Farnsworth

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