Review request for JMC-6492: Add unit support for jdk.jfr.Frequency

[Erik Gahlin]

Frequency can also be used in combination with DataAmount.

For example, the Network Utilization event can have a rate of 100 Mbps 
using the annotations @Frequency @DataAmount(DataAmount.BITS) in 
combination.

I am thinking of adding two units, Frequency.HERTZ and 
Frequency.PER_SECOND.

Question is, what should be the default?

I'm leaning towards PER_SECOND as it seems more common. This is not for 
JDK 13, as it requires a CSR request and some bake time.

Erik

> Hi Jie,
>
> On Wed, May 29, 2019 at 9:36 AM Jie Kang <jkang at redhat.com> wrote:
>
>> Hi,
>>
>> The attached patch adds a case for contentType "hertz",  annotation
>> "jdk.jfr.Frequency" used in JFR events like CPUTimeStampCounter, to
>> use the Hertz unit introduced in JMC-5768.
>>
>> The following is a before and after image for the event browser for
>> CPUTimeStampCounter
>> https://imgur.com/a/cSVlmOM
>>
>> How does it look?
>>
> This looks good to me.
>
> Just a note from playing around with the patch, CPUTimeStampCounter was
> updated in changeset 2cf5bec8d8ba [0] to use hertz instead of frequency per
> second. As a result, older recordings will still show their numerical value
> as per their jfr file, but newer recordings will now correctly use the hz
> unit.
>
>
>>
>> Regards,
>>
> Cheers,
>
> Alex
>
> [0] http://hg.openjdk.java.net/jdk-updates/jdk11u/rev/2cf5bec8d8ba