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

Vincenzo Frascino
2018-12-11T13:25:16Z

On 29/11/2018 22:41, Thomas Gleixner wrote:
> 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.
>

As you pointed out I followed the pattern of core timekeeper, but looking at it
after your comment, it seems obvious that one is enough.

> Thanks,
>
> tglx
>

--
Regards,
Vincenzo