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SubjectRe: [patch 1/3] sched_clock: document 4Mhz vs 1Mhz decision

* akpm@linux-foundation.org <akpm@linux-foundation.org> wrote:

> From: Stephen Boyd <sboyd@codeaurora.org>
> Subject: sched_clock: document 4Mhz vs 1Mhz decision
>
> Bo Shen sent a patch to change this to 1Mhz instead of 4Mhz but according
> to Russell King the use of 4Mhz was intentional. Add a comment to this
> effect so that others don't try to change the code as well.
>
> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
> Cc: Bo Shen <voice.shen@atmel.com>
> Cc: Russell King <rmk@arm.linux.org.uk>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> kernel/time/sched_clock.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff -puN kernel/time/sched_clock.c~sched_clock-document-4mhz-vs-1mhz-decision kernel/time/sched_clock.c
> --- a/kernel/time/sched_clock.c~sched_clock-document-4mhz-vs-1mhz-decision
> +++ a/kernel/time/sched_clock.c
> @@ -132,6 +132,10 @@ void __init sched_clock_register(u64 (*r
> clocks_calc_mult_shift(&cd.mult, &cd.shift, rate, NSEC_PER_SEC, 3600);
>
> r = rate;
> + /*
> + * Use 4MHz instead of 1MHz so that things like 1.832Mhz show as
> + * 1832Khz
> + */
> if (r >= 4000000) {
> r /= 1000000;
> r_unit = 'M';

Instead of magic precision cutoff limits the better solution would be
to simply display not just decimal part but also the first 3 digits of
the fractional part:

1.123 Hz
990.134 kHz
1.832 MHz
12.314 GHz

etc. - then every number could be displayed in its natural unit
without magic precision limits.

It would also be mostly self-documenting.

Thanks,

Ingo


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