Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings

From: Peter Zijlstra
Date: Wed Jan 20 2016 - 15:20:27 EST

On Wed, Jan 20, 2016 at 08:57:06PM +0100, Thomas Gleixner wrote:
> > Here too, ktime_get() is daft.
> What's the problem? ktime_xxx() itself or just the clock monotonic variant?
> On 99.9999% of the platforms ktime_get_mono_fast/raw_fast is not any slower
> than sched_clock(). The only case where sched_clock is faster is if your TSC
> is buggered and the box switches to HPET for timekeeping.

The HPET thing, I just don't want to have to explain why this is so much
more expensive on some random weird machine, esp. since it really
doesn't matter.