Re: [PATCH v2 04/28] kernel: Add masks support for Raw and NTP time

Thomas Gleixner
2018-11-29T22:41:26Z

On Thu, 29 Nov 2018, Vincenzo Frascino wrote:

> Depending on the clocksource selected there can be supported a
> different resolution hence we require a mask to be applied to the
> time calculation.
>
> This patch exposes the mask in the datapage for Raw and NTP adjusted
> clock.
>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> ---
> include/vdso/datapage.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
> index d50a108afaed..0a7bdccf5773 100644
> --- a/include/vdso/datapage.h
> +++ b/include/vdso/datapage.h
> @@ -34,6 +34,8 @@ struct vdso_data {
> __u64 wtm_clock_nsec;
> __u64 btm_nsec; /* Monotonic to boot time */
> __u64 tai_sec; /* International Atomic Time */
> + __u64 cs_mono_mask; /* NTP-adjusted clocksource mask */
> + __u64 cs_raw_mask; /* Raw clocksource mask */

And why would they be different? The core timekeeper has them duplicated
purely for access pattern optimization and simplicity.

Thanks,

tglx