On Wed, 21 Sep 2016, Nicolai Stange wrote:
> Thomas Gleixner <t...@linutronix.de> writes:
> > Have you ever measured the overhead of the extra work which has to be done
> > in clockevents_adjust_all_freqs() ?
>
> Not exactly, I had a look at its invocation frequency which seems to
> decay exponentially with uptime, presumably because the NTP error
> approaches zero.
>
> However, I've just gathered a function_graph ftrace on my Intel
> i7-4800MQ (Haswell, 8HTs):
>
> # TIME CPU DURATION FUNCTION CALLS
> # | | | | | | | |
> 85.287027 | 0) 0.899 us | clockevents_adjust_all_freqs();
> 85.288026 | 0) 0.759 us | clockevents_adjust_all_freqs();
> 85.289026 | 0) 0.735 us | clockevents_adjust_all_freqs();
> 85.290026 | 0) 0.671 us | clockevents_adjust_all_freqs();
> 149.503656 | 2) 2.477 us | clockevents_adjust_all_freqs();
That's not that bad. Though I'd like to see numbers for ARM (especially the
less powerful SoCs) as well.
Thanks,
tglx
