high precision timers

high precision timers

[Hyeonggon Yoo]

the 'timer wheel' - which has low resolution works at jiffy resolution.
so usually it has precision of 1~10ms.

and there's high resolution timers in kernel to have nanosecond resolution,
but it doesn't seem to have nanosecond precision

is there a way to deal with high precision timers in kernel?
does it require specific hardware?

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Re: high precision timers

[Greg KH]

On Sun, May 02, 2021 at 11:10:11PM +0900, Hyeonggon Yoo wrote:
> the 'timer wheel' - which has low resolution works at jiffy resolution.
> so usually it has precision of 1~10ms.
> 
> and there's high resolution timers in kernel to have nanosecond resolution,
> but it doesn't seem to have nanosecond precision
> 
> is there a way to deal with high precision timers in kernel?

What exactly are you needing here?  And do you have hardware that
provides both high precision and high resolution?

thanks,

greg k-h

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Re: high precision timers

[Valdis Klētnieks]

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On Mon, 03 May 2021 00:56:17 +0900, Hyeonggon Yoo said:

> I mean, is there an API that guarantees high precision (non architecture
> dependent way)

How do you guarantee high precision if you're on hardware that doesn't
provide a high precision/resolution timer?

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Re: high precision timers

[loïc tourlonias]

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Hi

On Mon, May 3, 2021 at 2:16 PM Hyeonggon Yoo <42.hyeyoo@gmail.com> wrote:

> Greg, and Valdis Thank you so much! It helped a lot!
>
> I thought there would be a way to do it because of high resolution.
>
> 2021년 5월 3일 (월) 오후 8:13, Valdis Klētnieks <valdis.kletnieks@vt.edu>님이 작성:
>
>> On Mon, 03 May 2021 00:56:17 +0900, Hyeonggon Yoo said:
>>
>> > I mean, is there an API that guarantees high precision (non architecture
>> > dependent way)
>>
>> How do you guarantee high precision if you're on hardware that doesn't
>> provide a high precision/resolution timer?
>>
>
If you don't have any hardware support, the Linux kernel can't magically
count faster than its system tick. ^^


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