arm: Replace arm sched_clock by clocksource based sched_clock
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Cover letter [patch 00/16] arm: Replace arm sched_clock by clocksource based sched_clock
Quoted 21 lines · Thomas Gleixner
Quoted 13 lines · Linus Walleij
2011/4/29 Thomas Gleixner <[email protected]>:
Quoted 6 lines · Tony Lindgren
Quoted 2 lines
What about
PRINTK_TIME? I think that usessched_clockright from the start.Right, but where is the problem ? A few time stamps with jiffies resolution and then the finegrained ones.
Jonas ?berg 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.
Quoted 5 lines
If we need more finegrained
sched_clock()before the clocksource is up, a good approach would be to utilize something like that forsched_clockup to that point, plus it has the upside that [0.000000] is as close to electrical power-on as possible.
Quoted 3 lines
Well, you can read out that value at the point the clocksource gets installed so you have the time spent up to that point without adding another facility, level of indirection ...
I think the problem here too is that we are calling read_persistent_clock and sched_clock before they're initialized. So we should default to jiffies based value before the platform code enables the hardware.
Tony