[patch 00/16] arm: Replace arm sched_clock by clocksource based sched_clock

[Linus Walleij]

2011/4/29 Thomas Gleixner <tglx at linutronix.de>:
> On Fri, 29 Apr 2011, Tony Lindgren wrote:
>> What about PRINTK_TIME? I think that uses sched_clock right from the
>> start.
>
> Right, but where is the problem ? A few time stamps with jiffies
> resolution and then the finegrained ones.

Jonas Åberg has this pending patch that we call "boot time recorder".
What it does is basically start a free running timer before the
kernel is booted, e.g. in U-boot or even in the ROM of your
machine if you can.

If we need more finegrained sched_clock() before the
clocksource is up, a good approach would be to utilize
something like that for sched_clock up to that point, plus
it has the upside that [0.000000] is as close to electrical
power-on as possible.

Yours,
Linus Walleij