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

Erik Gahlin erik.gahlin at
Wed Jun 5 16:18:28 UTC 2019

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 

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

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.


> Hi Jie,
> On Wed, May 29, 2019 at 9:36 AM Jie Kang <jkang at> 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
>> 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]

More information about the jmc-dev mailing list