Re: TSC improvement

[Masanobu SAITOH <msaitoh%execsw.org@localhost>]

Hi.

On 2020/06/10 4:37, Joerg Sonnenberger wrote:
> On Tue, Jun 09, 2020 at 05:16:27PM +0000, Taylor R Campbell wrote:
>> It's great to see improvements to our calibration of the TSC (and I
>> tend to agree that cpu_counter should be serializing, so that, e.g.,
>> cpu_counter(); ...; cpu_counter() reliably measures time taken in the
>> ellipsis).
> 
> I'm pretty sure we want to have both variants.
> 
> Joerg

You mean we should have both cpu_counter() and cpu_counter_serializing()
(or cpu_counter() and cpu_counter_unserializing())? If so, why?

I have no strong opinion about this. When I wrote that change, I added
cpu_counter_serializing(). We already have tsc_get_timecount(), cpu_counter()
and cpu_counter32() as MI API. In addition, x86 also has rdtsc(and will
have some serializing functions). There are so many similar functions,
so I thought it would be good to avoid code duplication and to be simple.

-- 
-----------------------------------------------
                SAITOH Masanobu (msaitoh%execsw.org@localhost
                                 msaitoh%netbsd.org@localhost)