linux-kernel - Re: slow down printk during boot.

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Date:	Thu, 05 Jul 2007 20:49:03 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Randy Dunlap <rdunlap@...otime.net>
Subject: Re: slow down printk during boot.

Dave Jones wrote:
> This patch from Randy has proven quite useful from time to time,
> and has been in Fedora kernels for a while for that reason.
> I fixed up some checkpatch warnings, and rediffed it a bunch
> of times, Randy did the heavy lifting.
> 
> ---
> 
> This one delays each printk() during boot by a variable time
> (from kernel command line), while system_state == SYSTEM_BOOTING.
> Caveat:  it's not terribly SMP safe or SMP nice.
> Any ideas for improvements (esp. in the SMP area) are appreciated.
> 
> ---
> 
> From: Randy Dunlap <rdunlap@...otime.net>
> 
> Optionally add a boot delay after each kernel printk() call,
> crudely measured in milliseconds, with a maximum delay of
> 10 seconds per printk.
> 
> Enable CONFIG_BOOT_DELAY=y and then add (e.g.):
> "lpj=loops_per_jiffy boot_delay=100"
> to the kernel command line.
> 
> Signed-off-by: Randy Dunlap <rdunlap@...otime.net>
> Signed-off-by: Dave Jones <davej@...hat.com>
> 
> ---
> 
>  init/calibrate.c  |    2 +-
>  init/main.c       |   25 +++++++++++++++++++++++++
>  kernel/printk.c   |   33 +++++++++++++++++++++++++++++++++
>  lib/Kconfig.debug |   18 ++++++++++++++++++
>  4 files changed, 77 insertions(+), 1 deletion(-)

hey, that's pretty neat.

I've occasionally hand-hacked something similar, to achieve those effects.

	Jeff



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